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PubMed1992

Disruptions in intracellular membrane trafficking and structure preclude the glucocorticoid-dependent maturation of mouse mammary tumor virus proteins in rat hepatoma cells.

We have previously shown that glucocorticoids regulate the trafficking and processing of mouse mammary tumor virus (MMTV) proteins in viral-infected M1.54 rat hepatoma cells. To examine the role of intracellular membrane integrity on MMTV protein maturation, brefeldin A (BFA) was utilized to disrupt membrane flow between the endoplasmic reticulum and Golgi. Immunoprecipitation and immunofluorescence microscopy revealed that in the presence of dexamethasone, BFA inhibited the proteolytic processing, cell surface delivery, and externalization of MMTV glycoproteins. Glycosidase digestion and inhibitors of protein glycosylation confirmed that the observed differences in apparent sizes of MMTV glycoprotein products are due to BFA-induced changes in oligosaccharide processing. BFA treatment inhibited the proteolytic processing of the MMTV phosphoprotein precursor, which normally associates with the cytoplasmic face of intracellular membranes. Similarities in salt extraction efficiency revealed that BFA did not affect the membrane affinity of the uncleaved phosphorylated precursor. In a complementary approach, proteolytic processing of the phosphorylated polyprotein did not occur in glucocorticoid-treated HTC cells transfected with a mutant MMTV provirus encoding a normal phosphorylated precursor, but which express a truncated MMTV glycoprotein missing its transmembrane domain and cytoplasmic tail. These results suggest that the MMTV glycoproteins and phosphoproteins may interact at a late step in the transport pathway in a manner required for their mutual processing in response to glucocorticoids and establishes the importance of functional interactions with intracellular membranes for maturation of the cytoplasmic MMTV phosphoproteins.

Animals↗

PubMed2025

Use of the D4H Probe to Track Sterols in Yeast.

Cholesterol is a fundamental component of cellular membranes, and its organization, distribution, and recycling are tightly regulated. Cholesterol can form, together with other lipids and proteins, membrane nanodomains, which play important roles in membrane trafficking, the spatiotemporal organization of signal transduction, or the modulation of plasma membrane transporters, among others. Not surprisingly then, the misregulation of cholesterol biosynthetic and transport pathways has been related to numerous diseases, including neurodegenerative and metabolic disorders. Here, we focus on the cholesterol-binding domain 4 (D4) of perfringolysin O (PFO, theta toxin) and its use as a probe to define the dynamics and subcellular localization of yeast sterols using time-lapse live-cell fluorescence microscopy. In combination with drugs that acutely interfere with sterol synthesis, such as terbinafine, the probe can also be used to monitor in real-time the extraction of sterols from specialized endoplasmic reticulum subdomains named ERSES (endoplasmic reticulum sterol exit sites) by the OSBP-related protein Osh2.

Saccharomyces cerevisiae↗

PubMed1992

Identification of rab2 as a tubulovesicle-membrane-associated protein in rabbit gastric parietal cells.

Rab proteins, which are ras-like low-molecular-mass GTP-binding proteins, are postulated to act as specific regulators of membrane trafficking in exocytosis and endocytosis. Previously, we reported a 23 kDa tubulovesicle-associated GTP-binding protein in rabbit gastric parietal cells [Basson, Goldenring, Tang, Lewis, Padfield, Jamieson & Modlin (1991) Biochem. J. 279, 43-48]. The major component of the 23 kDa protein is now identified as rab2. Rab2 was co-localized in tubulovesicle membranes from parietal cells. Consistent with GTP-binding activity (as documented before), upon maximal stimulation of parietal cells, rab2 immunoreactivity was redistributed from a 50,000 g to a 4000 g subcellular membrane fraction. The tubulovesicle-associated rab2 behaved as an integral membrane protein, since both 0.5 M-NaCl and 0.1 M-carbonate extraction failed to remove the protein from the tubulovesicle membrane. Utilizing a PCR the rab2 cDNA sequence from rabbit parietal cells was obtained, and it showed only one amino acid difference compared with the human sequence. The results of the present study provide strong evidence that parietal cells possess a rab2 protein which is tightly associated with tubulovesicle membranes.

Adenosine Triphosphatases↗

PubMed2025

FTO promotes weight gain via altering Kif1a splicing and axonal vesicle trafficking in AgRP neurons.

N6-methyladenosine (m6A) is an abundant chemical RNA modification involved in the regulation of many biological processes. The m6A demethylase FTO (fat mass and obesity-associated protein) is known to affect body weight, but its systemic context and underlying mechanisms remain unclear. Here, we found that mice lacking or overexpressing Fto in agouti-related peptide-expressing (AgRP) neurons in the hypothalamus exhibited decreased and increased body weight, respectively. FTO demethylated m6A on mRNAs for proteins associated with membrane trafficking and alternative splicing in AgRP neurons. Downstream, FTO-modulated alternative splicing of the axonal motor protein Kif1a affected its hinge region, which is relevant to the structure and function of KIF1A. Notably, Kif1a knockdown in AgRP neurons suppressed the weight gain of mice overexpressing Fto. In addition, FTO increased the trafficking and secretion of dense-core vesicles containing neuropeptides NPY and AgRP from AgRP neurons. Collectively, these results reveal a novel regulatory FTO-KIF1A axis in the brain affecting appetite-stimulating AgRP neurons and systemic energy homeostasis, via FTO regulation of the epitranscriptome of AgRP neurons.

Animals↗

PubMed2026

Disruption of Polycystin Ciliary Localization and Channel Function by Autosomal Dominant Polycystic Kidney Disease-Causing Polycystin-1 Variants.

KEY POINTS: We developed assays to measure genetic variant effects on polycystin-1, the protein mutated in most autosomal dominant polycystic kidney disease. All tested pathogenic variants disrupted either polycystin-1 ciliary trafficking or channel function. Trafficking and channel function of some pathogenic variants was restored by low temperature culture to promote polycystin folding. BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the leading monogenic cause of kidney failure and affects millions of people worldwide. Despite the prevalence of ADPKD, limited mechanistic understanding has hindered therapeutic development. Most ADPKD is caused by loss-of-function variants in polycystin-1 (PC1). METHODS: We developed assays that quantify the effect of nontruncating variants on PC1 ciliary localization, membrane trafficking, and polycystin channel function. RESULTS: We evaluated 29 nontruncating variants in PC1 and found that pathogenic variants disrupt two molecular phenotypes: ( 1 ) localization of PC1 at the primary cilium or ( 2 ) polycystin ion channel activity. Ciliary localization of a subset of polycystin variants was restored when cells were cultured at low temperature. A subset of variants with localization restored by low temperature formed functional channels. CONCLUSIONS: This study demonstrated that disruptions in polycystin ciliary trafficking and channel function are common causes of ADPKD. Defects in ciliary trafficking and channel function can be rescued for a subset of pathogenic variants, establishing a foundation for polycystin-targeted therapies in ADPKD.

Polycystic Kidney, Autosomal Dominant↗

PubMedDate not supplied

Small GTP-binding proteins in parietal cells: candidate modulators of parietal cell membrane dynamics.

The stimulated fusion of intracellular H/K-ATPase-containing tubulovesicles with a target canalicular membrane surface is central to the process of acid secretion. A super-family of small GTP-binding proteins (smGTPBPs) has been implicated in many aspects of intracellular dynamics and vesicle membrane trafficking. We have investigated the presence of smGTPBPs in isolated rabbit parietal cells. Parietal cells possess a number of smGTPBP species with molecular masses of 18-28 kDa. One 23 kDa smGTPBP has been localized to tubulovesicles and identified immunochemically as rab2. Rab2 redistributes during stimulation in concert with the movement of the H/K-ATPase. The results demonstrate that specific smGTPBPs are associated with the parietal cell secretory apparatus. Small GTP-binding proteins are important candidate regulators of parietal secretory membrane dynamics.

Animals↗

PubMed2026

Early-Onset Retinopathy in Patients With Variants in SLC6A6 Leading to Impaired Taurine Transport.

IMPORTANCE: Inherited retinal dystrophies are a group of disorders that may lead to progressive vision loss. Improved knowledge of their molecular genetics is important for accurate diagnosis or development of targeted therapies. OBJECTIVE: To identify pathogenic variants in the SLC6A6 gene (encoding TauT, the main transporter for taurine) and assess their role in the molecular pathogenesis of hereditary early-onset retinal dystrophy (EORD) in affected individuals from diverse ethnic backgrounds. DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective, multicenter observational study conducted between June 2019 and March 2025, involving 7 affected and 10 unaffected individuals from 4 unrelated families recruited in Pakistan, Italy, the US, and France. EXPOSURE: Pathogenic variants in SLC6A6 in individuals with EORD. MAIN OUTCOMES AND MEASURES: Genetic, clinical, and functional outcomes of pathogenic variants in SLC6A6 in individuals with Leber congenital amaurosis (LCA) and EORD. All patients underwent standard clinical examinations, including visual acuity, full-field electroretinography, and multimodal retinal imaging, followed by measurement of fasting plasma taurine levels. In vitro and ex vivo taurine transport and membrane trafficking assays in human embryonic kidney (HEK)-293 cells, as well as patient-derived fibroblasts, were also performed. RESULTS: All 7 affected individuals exhibited LCA/EORD, with extraocular findings in some. Genetic analysis identified homozygous pathogenic SLC6A6 variants in all affected individuals, while unaffected relatives were heterozygous carriers. Families 1 and 2 carried missense variants p.(Thr249Ile) and p.(Ala294Thr), while families 3 and 4 carried truncating variants-a deletion of exon 11 and p.(Thr113Ter), respectively. Functional studies demonstrated that both missense variants are associated with complete loss of taurine transport in HEK-293 cells and patient-derived fibroblasts. Additionally, irrespective of the variants considered, plasma taurine levels in affected individuals were reduced compared with heterozygous carriers (difference between means, -31.7 µmol/L; 95% CI, -42.7 to -20.8; P < .001) and healthy control individuals (difference between means, -37.7 µmol/L; 95% CI -41.6 to -33.8; P < .001). CONCLUSIONS AND RELEVANCE: These findings confirm and expand the role of biallelic variants in SLC6A6 in association with LCA/EORD due to impaired taurine transport. These findings suggest that patients with a diagnosis of SLC6A6-related LCA/EORD may be candidates for investigational oral taurine supplementation.

Humans↗

PubMed2025

CRISPR/Cas9 screenings reveal the role of STX1A and CDK1 in Cathepsin G entering and killing colorectal cancer cells.

Neutrophils are the major populations of white blood cells and have been reported to facilitate cancer metastasis. Meanwhile, emerging evidence has recently suggested the anti-cancer role of neutrophils. Our previous study revealed that CB-839 and 5-FU-treated colorectal cancer (CRC) tumors recruited neutrophils and induced neutrophil extracellular traps (NETs). Cathepsin G (CTSG), which is released during NET formation, enters CRC cells through the receptor for advanced glycation end products (RAGE) and cleaves 14-3-3ε to promote apoptosis. However, the detailed mechanism underlying CTSG's anti-tumor function remains less studied. In this study, we report that CTSG enters CRC cells through RAGE-mediated endocytosis. Knocking out RAGE or inhibiting endocytosis blocks CTSG from entering CRC cells and attenuates CTSG-induced apoptosis. Furthermore, the clathrin coat assembly complex and SNARE proteins were enriched in an arrayed CRISPR/Cas9 screening targeting human membrane trafficking genes. Knocking out SNARE protein STX1A prevents the spread of CTSG in CRC cells and the induction of cleaved PARP. A pooled genome-wide CRISPR/Cas9 screening further identifies the role of CDK1 in the NET-induced killing of CRC cells. Inhibiting CDK1 protected CRC cells from killing by CTSG. Our study reveals novel mechanisms by which CTSG enters and kills CRC cells.

CDK1↗

PubMed2026

A subcomplex comprising TRAPPC11, TRAPPC12, TRAPPC13 and the fungal TRAPPC2L homolog, Tca17, directs TRAPPIII to autophagy.

Transport protein particle complexes (TRAPPs) are master regulators of membrane trafficking. TRAPPs are targeted to different locales by pathway-specific subunits decorating a core hetero-heptamer to build TRAPPII (Golgi exit) and TRAPPIII (autophagosomes and ER-Golgi trafficking). Metazoan and Arabidopsis TRAPPIII have three components, TRAPPC11, TRAPPC12 and TRAPPC13 (hereafter denoted TRAPPC11/12/13), that are absent from budding yeast. We studied TRAPPC11/12/13 in the related ascomycete Aspergillus nidulans, where TRAPPC11 and TRAPPC12 localize to pre-autophagosomes and their ablation impairs autophagy. We found that two stable subcomplexes containing Tca17, the homolog of metazoan TRAPPC2L, coexist - one includes the TRAPPII-specific subunits Trs120, Trs130 and Trs65 whereas the other contains the TRAPPIII-specific subunits TRAPPC11/12/13. Both are recruited to core TRAPP by Tca17, which therefore plays a crucial role by determining the physiological role of TRAPP. TRAPPIII also exists in two versions, TRAPPIIIa and TRAPPIIIb, both of which contain Trs85, the homolog of metazoan TRAPPC8, but with only TRAPPIIIb containing TRAPPC11/12/13, which target TRAPPIII to autophagy. This study might help characterize potentially pathogenic mutations affecting human TRAPPC11/12/13, facilitating assessment of their functional consequences in a genetically amenable ascomycete.

Autophagy↗

PubMed2025

Genome-wide identification of modulators of Chlamydia trachomatis parasitophorous vacuole stability highlights an important role for sphingolipid supply.

A mechanistic understanding of how intracellular pathogens evade the intrinsic defenses of their host cells could open up intriguing therapeutic opportunities. Here, we applied a genome-wide genetic screening approach to investigate the nature of the defensive host cell death response suppressed by the membrane trafficking modulator CpoS, an effector protein secreted by the obligate intracellular bacterial pathogen Chlamydia trachomatis. Initially, this work revealed a CpoS-deficient mutant to exhibit a markedly increased dependence on host cellular synthesis of ceramides, the precursors of complex sphingolipids. Using novel microscopic reporters, we then established CpoS' role in defense evasion to occur by preserving the integrity of Chlamydia's parasitophorous vacuole (the inclusion) via ensuring an adequate sphingolipid supply. More specifically, we observed CpoS deficiency to destabilize inclusions, initially characterized by a release of individual bacteria into the host cell cytosol, then followed by inclusion rupture concomitant with host cell death. Exogenous addition of sphingosine stabilized CpoS-deficient inclusions, whereas disruption of host cellular ceramide synthesis destabilized wild-type inclusions. In combination, CpoS deficiency and impaired ceramide synthesis - presumably disrupting both Chlamydia's vesicular and non-vesicular sphingolipid supply routes - destabilized inclusions even earlier, resulting in infection clearance and host cell survival rather than host cell death. Overall, this study highlights how the vacuolar pathogen C. trachomatis maintains vacuole integrity by ensuring a steady sphingolipid supply, potentially offering inspiration and directions for future therapeutic strategies targeting parasitophorous vacuoles.

Chlamydia trachomatis↗

PubMed2026

Stepwise Humanization of the Yeast TRAPP Core Enables Functional Analysis of TRAPP Variants.

The Transport Protein Particle (TRAPP) complex is a highly conserved multi-subunit tethering complex that plays a critical role in membrane trafficking. Mutations in TRAPP complex subunits have been implicated in a growing spectrum of rare genetic disorders, yet the molecular mechanisms underlying variant pathogenicity often remain unclear. Here, we developed a humanized yeast platform to enable systematic functional characterization of TRAPP complex variants of uncertain significance. Using a stepwise gene replacement strategy in Saccharomyces cerevisiae, we constructed a strain in which five yeast TRAPP core subunits were replaced with their human orthologues. The integration of human subunits was validated through quantitative RT-PCR and Western blotting. Growth assays revealed that partial humanization of the core complex recapitulates key functional aspects of TRAPP assembly and enables the functional investigation of variants of uncertain significance in vivo. Structural modeling and clash analysis provided insights into the impact of specific mutations on complex stability and subunit interactions. TRAPPC3 has not yet been definitively associated with human disease. Introduction of TRAPPC3 variants of uncertain clinical significance into the humanized strain resulted in pronounced growth defects and predicted structural clashes. This work demonstrates the power of humanized yeast as a model for elucidating potential genotype-phenotype relationships in TRAPPopathy disorders and provides a versatile platform to support variant interpretation, mechanistic studies, and potential therapeutic screening.

Saccharomyces cerevisiae↗

PubMed1992

Calcium-binding proteins: basic concepts and clinical implications.

Calcium ions exert their effects in part via interactions with a wide variety of intracellular calcium-binding proteins. One class of these proteins shares a common calcium-binding motif, the EF-hand. A consensus amino acid sequence for this motif has aided the identification of new members of this family of EF-hand proteins, which now has over 200 members. A few of these proteins are present in all cells, whereas the vast majority are expressed in a tissue-specific fashion. The physiological function of a few of these proteins is known to be achieved via a calcium-dependent interaction with other proteins, thereby regulating their activity. Some members, like parvalbumin, calbindin, and calretinin, proved to be useful neuronal markers for a variety of functional brain systems and their circuitries. Their major role is assumed to be buffering, transport of Ca2+, and regulation of various enzyme systems. Since cellular degeneration is accompanied by impaired Ca2+ homeostasis, a protective role for Ca(2+)-binding proteins in certain neuron populations has been postulated. Another protein family are the annexins, members of which interact with phospholipids and cellular membranes in a calcium-dependent manner. In some cases members of the annexin family were even found to interact with EF-hand proteins. Certain annexins have been suggested to be involved in anti-inflammatory response, inhibition of blood coagulation, membrane trafficking or cytoskeletal organization, but several of these functions have been questioned recently. The elucidation of the interactions and functions of the majority of these proteins remains a challenging task for the coming years.

Animals↗

PubMed2026

Co-expression of the Mammaglobin (SCGB2A2) Gene With hsa-miR-184 and hsa-miR-190b Indicates Its Possible Role in Oncogenic Pathways in Breast Cancer.

BACKGROUND/AIM: Breast cancer is the most common cancer in women worldwide, and early detection remains a significant challenge. Recent studies have identified increased expression of Mammaglobin A (Q13296, Gene: SCGB2A2) mRNA in breast cancer, suggesting its potential as a disease marker, although its function is not fully understood. To elucidate Mammaglobin's role, this study sought to identify co-expressed miRNAs and analyze the biological pathways they regulate. MATERIALS AND METHODS: Using TCGAbiolinks and Firebrowse, miRNA and gene expression data were collected from 86 patients, including tumor and normal tissue samples from the Cancer Genome Atlas (TCGA) Breast Cancer cohort. Transcriptomic data were analyzed with DESeq2, and a Spearman correlation was calculated for significant p-values, which were further explored using enrichment tools and target gene databases. RESULTS: DESeq2 was used to identify differential expression of miRNAs between normal and tumor breast tissues. Out of 782 miRNAs differentially expressed in breast cancer, hsa-mir-184 and hsa-mir-190b showed a significant positive correlation with SCGB2A expression. These markers were also upregulated in breast cancer tissues compared to normal tissues. Bioinformatics analysis revealed that hsa-mir-184 and hsa-mir-190b play important roles in cancer and cellular proliferation. These miRNAs target a wide range of genes, including sorting nexin 9 (SNX9) and annexin 6 (ANXA6), which are involved in membrane stability, vesicular trafficking, and cell mobility, and they contribute to cancer metastasis. CONCLUSION: The positive correlation among the expression of hsa-miR-184, hsa-miR-190b, and SCGB2A2 suggests that they may participate in shared biological pathways. These pathways govern critical cellular processes, such as membrane trafficking and cell signaling, which are frequently disrupted in cancer. Consequently, these findings enable a better understanding of the role of Mammaglobin in breast cancer signaling.

MicroRNAs (miRNAs)↗

PubMed2026

The msf gene causes condition-specific shifts in global gene expression in Haemophilus influenzae.

UNLABELLED: Haemophilus influenzae is a diverse human-restricted bacterium that normally colonizes the healthy nasopharynx but also causes common infections. Comparisons of clinical isolate genomes previously identified a gene, msf, that contained Sel1-like repeats that were associated with clinical disease. Mutant analysis had further found that msf improved survival in macrophages and increased systemic infection in an animal model. However, the role of msf in other conditions and its molecular function remain unknown. To identify protein-protein interactions with Msf, a yeast two-hybrid screen against an H. influenzae prey library was conducted, which found potential interactions with lipoprotein exporter protein LolD and an autotransporter adhesin Hap. To identify effects of msf on gene expression, we compared wild-type and mutant strains grown in multiple culture conditions by RNA-seq. The results indicate that msf modulates global gene expression in a condition-dependent manner, exerting an especially strong influence in starved surface-attached biofilm cells. The few consistent changes in mutants' planktonic exponential and stationary phases included decreased expression of two paralogous autotransporter adhesins. By contrast, mutant cells in starved surface-attached biofilms had dramatic changes in expression, including upregulation of protein translation and downregulation of alternative carbon metabolism. However, assays of 24 hour biofilm phenotypes found only subtle gene expression changes. Together, the results point to a speculative model of Msf functioning as an envelope-associated chaperone whose presence affects the relative expression of proteins at the outer membrane. IMPORTANCE: Comparing genomes from different clinical isolates of the same pathogenic bacterial species has identified genes associated with virulence, but many of these are understudied or have no known function. The msf gene was previously implicated as a virulence factor in Haemophilus influenzae, a common cause of mucosal diseases including middle-ear and chronic lung infections. This study finds that the msf gene causes condition-specific changes in gene expression, with especially dramatic changes in starved surface-attached biofilm cells. Along with identification of putative protein-protein interaction partners, the results provide new clues as to the molecular and cellular function of Msf, potentially as an envelope-associated chaperone involved in membrane protein trafficking. Understanding how virulence-associated genes like msf modulate bacterial responses to the environment may help explain why some bacterial strains remain harmless colonizers while others become pathogens.

Haemophilus influenzae↗

PubMed2026

Deciphering the Protein Phosphorylation Dynamics Triggered by Seconds of Force Stimulation.

Plants perceive mechanical forces through phosphosignaling networks, but their relationship with gravity signaling remains elusive. To dissect gravity force signaling components, we performed SILIA-based phosphoproteomics on Arabidopsis aerial organs subjected to 20-s inversion or 30-s gravistimulation, identifying 2,733 and 2,878 phosphoproteins, respectively. Quantitative analysis revealed 34 significantly regulated phosphoproteins specific to inversion and 52 specific to gravistimulation. Inversion-specific phosphoproteins, associated with the initial calcium code, likely mediate calcium signals through EF-hand proteins, CPK1, and calmodulin-interacting proteins, potentially intersecting with receptor-like kinase-initiated MAPK cascades via RAF15 and MKK1/2 to induce gravitropic responses. Gravistimulation-specific phosphoproteins, linked to the secondary calcium code, function in calcium signaling/homeostasis (ACA8, ZAC, IQD2, ANNAT1), membrane vesicle trafficking (ABCG36, ARF-GAP8), and lipid signaling (PIP5K8/9), supporting auxin transport and stress signal transduction. Immunoblot validation confirmed treatment-associated phosphosites pS108-PATL3 and pS107-TREPH2, along with inversion-specific pS1145-ATEH2, exhibiting stem-specific phosphorylation enhancement and force-discriminatory responses. Functional analysis identified the integrin-like protein GREPH1 as a key gravitropism regulator, with greph1 mutants displaying reduced inflorescence stem gravicurvature. Notably, hyperphosphorylation of pS107-TREPH2 and pS1145-ATEH2 peaked at 20 to 50 s in greph1 mutants but persisted from 20 s to 2 h in WT plants. These findings establish a stem-enriched phosphorylation code for gravity force discrimination, with GREPH1 modulating spatiotemporal phosphoprotein dynamics and shoot gravicurvature, potentially functioning as a receptor reminiscent of sedimenting plastids.

Arabidopsis↗

PubMed2026

Expanding the genotypic and phenotypic spectrum of PGAP1 deficiency: clinical and functional insights from 15 patients.

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are essential for neuronal development, synaptic organization and signaling. Defects in GPI-anchor biosynthesis or remodeling cause rare neurodevelopmental disorders, including post-GPI attachment to proteins 1 (PGAP1) deficiency. PGAP1 encodes an inositol deacylase required for GPI-anchor remodeling and appropriate trafficking and membrane localization of GPI-APs. Loss of PGAP1 function disrupts GPI-AP processing, but the clinical spectrum remains incompletely defined because reported cohorts are small. We report 15 individuals with biallelic PGAP1 variants from 11 unrelated families identified through international collaboration. Clinical information was collected using a standardized phenotyping questionnaire and review of available clinical records. The most frequently recorded features were developmental delay or intellectual disability, motor developmental delay, speech impairment, facial dysmorphism, hypotonia and seizures. Independent walking was clearly recorded in a minority of individuals, while feeding, ophthalmological, musculoskeletal and neuroimaging findings were recorded in subsets of the cohort. Clinical investigations were performed as part of routine care and were not uniform across sites. Accordingly, source-dependent assessments including MRI, EEG, EMG/NCS, formal ophthalmology, hearing assessment, systemic imaging, IQ/DQ testing, MRC scoring and anthropometric Z-scores are reported descriptively or using available-data denominators. Spasticity, hypertonia or possible peripheral nerve involvement was recorded in some clinical summaries; however, electrophysiological confirmation was not uniformly available, and confirmed peripheral neuropathy was not analyzed as a cohort-level prevalence outcome. Functional studies in selected patient-derived cells or model systems demonstrated PI-PLC resistance of GPI-APs, supporting impaired GPI-anchor remodeling. These findings expand the genotypic and recorded phenotypic spectrum of PGAP1 deficiency.

Journal Article↗

PubMed2025

The Dynamics of the ESCRT Machinery in Open Mitosis from Physiology to Pathology.

The Endosomal Sorting Complex Required for Transport (ESCRT) is a highly conserved machinery best known for its role in endosomal trafficking and membrane remodeling. Increasing evidence shows that ESCRT components are also key regulators during open mitosis, where precise membrane dynamics are essential for nuclear envelope reformation and spindle disassembly. In this review, we explore how the ESCRT machinery coordinates mitotic processes under physiological conditions and how their dysregulation contributes to genomic instability, altered cell division, and disease. We highlight recent findings on the spatiotemporal control of ESCRT recruitment at mitotic membranes, the interplay with chromatin and nuclear envelope-associated factors, and the consequences of defective ESCRT function in pathological contexts such as cancer and neurodegeneration. By connecting molecular mechanisms with cellular outcomes, we provide an integrated view of how the ESCRT machinery acts as critical guardian of mitotic fidelity and offer some routes for the identification of potential therapeutic targets in human disease.

Humans↗

PubMed2026

Bi-allelic loss-of-function variants in JKAMP cause a neurodevelopmental syndrome associated with dysregulation of GPR37 trafficking.

The endoplasmic reticulum (ER) serves as a key hub for protein homeostasis, maintaining a strict quality-control system that ensures only properly folded proteins reach their destinations, while misfolded proteins are degraded via ER-associated degradation (ERAD) or selective ER-phagy. JKAMP, which encodes an ER-resident transmembrane protein involved in ERAD, has not previously been associated with human disease. Here, we report bi-allelic loss-of-function variants in JKAMP in 14 affected individuals from 10 unrelated families presenting with a neurodevelopmental syndrome characterized by intellectual disability, developmental delay, seizures, hypotonia, microcephaly, and dysmorphic features. An in vivo zebrafish model lacking jkamp recapitulated key aspects of the human disorder, including developmental abnormalities and impaired myelin production, further corroborating its pathogenic role. Mechanistic studies identified GPR37, a brain-enriched orphan G protein-coupled receptor (GPCR) and known JKAMP interactor, as a critical downstream effector. GPR37 plays essential roles in dopaminergic signaling, inflammatory pain regulation, neuroprotection, and myelination. Loss of JKAMP resulted in defective folding and degradation of GPR37, leading to its accumulation within the ER and impaired trafficking to the plasma membrane, likely due to impaired ER quality control. These findings establish JKAMP as a previously unrecognized contributor to human neurodevelopment and uncover a pathogenic mechanism linking ER protein quality control to GPCR regulation and neurological disease.

Humans↗