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At least 199 records · Page 11Linked to original sources
PubMed2005

The Rac activator Tiam1 controls tight junction biogenesis in keratinocytes through binding to and activation of the Par polarity complex.

The GTPases Rac and Cdc42 play a pivotal role in the establishment of cell polarity by stimulating biogenesis of tight junctions (TJs). In this study, we show that the Rac-specific guanine nucleotide exchange factor Tiam1 (T-lymphoma invasion and metastasis) controls the cell polarity of epidermal keratinocytes. Similar to wild-type (WT) keratinocytes, Tiam1-deficient cells establish primordial E-cadherin-based adhesions, but subsequent junction maturation and membrane sealing are severely impaired. Tiam1 and V12Rac1 can rescue the TJ maturation defect in Tiam1-deficient cells, indicating that this defect is the result of impaired Tiam1-Rac signaling. Tiam1 interacts with Par3 and aPKCzeta, which are two components of the conserved Par3-Par6-aPKC polarity complex, and triggers biogenesis of the TJ through the activation of Rac and aPKCzeta, which is independent of Cdc42. Rac is activated upon the formation of primordial adhesions (PAs) in WT but not in Tiam1-deficient cells. Our data indicate that Tiam1-mediated activation of Rac in PAs controls TJ biogenesis and polarity in epithelial cells by association with and activation of the Par3-Par6-aPKC polarity complex.

Animals↗
PubMed2007

Puf3p, a Pumilio family RNA binding protein, localizes to mitochondria and regulates mitochondrial biogenesis and motility in budding yeast.

Puf3p binds preferentially to messenger RNAs (mRNAs) for nuclear-encoded mitochondrial proteins. We find that Puf3p localizes to the cytosolic face of the mitochondrial outer membrane. Overexpression of PUF3 results in reduced mitochondrial respiratory activity and reduced levels of Pet123p, a protein encoded by a Puf3p-binding mRNA. Puf3p levels are reduced during the diauxic shift and growth on a nonfermentable carbon source, conditions that stimulate mitochondrial biogenesis. These findings support a role for Puf3p in mitochondrial biogenesis through effects on mRNA interactions. In addition, Puf3p links the mitochore, a complex required for mitochondrial-cytoskeletal interactions, to the Arp2/3 complex, the force generator for actin-dependent, bud-directed mitochondrial movement. Puf3p, the mitochore, and the Arp2/3 complex coimmunoprecipitate and have two-hybrid interactions. Moreover, deletion of PUF3 results in reduced interaction between the mitochore and the Arp2/3 complex and defects in mitochondrial morphology and motility similar to those observed in Arp2/3 complex mutants. Thus, Puf3p is a mitochondrial protein that contributes to the biogenesis and motility of the organelle.

Actin-Related Protein 2-3 Complex↗
PubMed2005

Alternative splicing suggests extended function of PEX26 in peroxisome biogenesis.

Matsumoto and colleagues recently identified PEX26 as the gene responsible for complementation group 8 of the peroxisome biogenesis disorders and showed that it encodes an integral peroxisomal membrane protein with a single C-terminal transmembrane domain and a cytosolic N-terminus that interacts with the PEX1/PEX6 heterodimer through direct binding to the latter. They proposed that PEX26 functions as the peroxisomal docking factor for the PEX1/PEX6 heterodimer. Here, we identify new PEX26 disease alleles, localize the PEX6-binding domain to the N-terminal half of the protein (aa 29-174), and show that, at the cellular level, PEX26 deficiency impairs peroxisomal import of both PTS1- and PTS2-targeted matrix proteins. Also, we find that PEX26 undergoes alternative splicing to produce several splice forms--including one, PEX26- delta ex5, that maintains frame and encodes an isoform lacking the transmembrane domain of full-length PEX26 (PEX26-FL). Despite its cytosolic location, PEX26- delta ex5 rescues peroxisome biogenesis in PEX26-deficient cells as efficiently as does PEX26-FL. To test our observation that a peroxisomal location is not required for PEX26 function, we made a chimeric protein (PEX26-Mito) with PEX26 as its N-terminus and the targeting segment of a mitochondrial outer membrane protein (OMP25) at its C-terminus. We found PEX26-Mito localized to the mitochondria and directed all detectable PEX6 and a fraction of PEX1 to this extraperoxisomal location; yet PEX26-Mito retains the full ability to rescue peroxisome biogenesis in PEX26-deficient cells. On the basis of these observations, we suggest that a peroxisomal localization of PEX26 and PEX6 is not required for their function and that the interaction of PEX6 with PEX1 is dynamic. This model predicts that, once activated in an extraperoxisomal location, PEX1 moves to the peroxisome and completes the function of the PEX1/6 heterodimer.

Alleles↗
PubMed1999

The role of the 3-hydroxy 3-methylglutaryl coenzyme A reductase cytosolic domain in karmellae biogenesis.

In all cells examined, specific endoplasmic reticulum (ER) membrane arrays are induced in response to increased levels of the ER membrane protein 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase. In yeast, expression of Hmg1p, one of two yeast HMG-CoA reductase isozymes, induces assembly of nuclear-associated ER stacks called karmellae. Understanding the features of HMG-CoA reductase that signal karmellae biogenesis would provide useful insights into the regulation of membrane biogenesis. The HMG-CoA reductase protein consists of two domains, a multitopic membrane domain and a cytosolic catalytic domain. Previous studies had indicated that the HMG-CoA reductase membrane domain was exclusively responsible for generation of ER membrane proliferations. Surprisingly, we discovered that this conclusion was incorrect: sequences at the carboxyl terminus of HMG-CoA reductase can profoundly affect karmellae biogenesis. Specifically, truncations of Hmg1p that removed or shortened the carboxyl terminus were unable to induce karmellae assembly. This result indicated that the membrane domain of Hmg1p was not sufficient to signal for karmellae assembly. Using beta-galactosidase fusions, we demonstrated that the carboxyl terminus was unlikely to simply serve as an oligomerization domain. Our working hypothesis is that a truncated or misfolded cytosolic domain prevents proper signaling for karmellae by interfering with the required tertiary structure of the membrane domain.

Carbocyanines↗
PubMed2001

Biogenesis of Golgi stacks in imaginal discs of Drosophila melanogaster.

We provide a detailed description of Golgi stack biogenesis that takes place in vivo during one of the morphogenetic events in the lifespan of Drosophila melanogaster. In early third-instar larvae, small clusters consisting mostly of vesicles and tubules were present in epithelial imaginal disk cells. As larvae progressed through mid- and late-third instar, these larval clusters became larger but also increasingly formed cisternae, some of which were stacked. In white pupae, the typical Golgi stack was observed. We show that larval clusters are Golgi stack precursors by 1) localizing various Golgi-specific markers to the larval clusters by electron and immunofluorescence confocal microscopy, 2) driving this conversion in wild-type larvae incubated at 37 degrees C for 2 h, and 3) showing that this conversion does not take place in an NSF1 mutant (comt 17). The biological significance of this conversion became clear when we found that the steroid hormone 20-hydroxyecdysone (ecdysone) is critically involved in this conversion. In its absence, Golgi stack biogenesis did not occur and the larval clusters remained unaltered. We showed that dGM130 and sec23p expression increases approximately three- and fivefold, respectively, when discs are exposed to ecdysone in vivo and in vitro. Taken together, these results suggest that we have developed an in vivo system to study the ecdysone-triggered Golgi stack biogenesis.

Animals↗
PubMed2007

Function of the Caenorhabditis elegans ABC transporter PGP-2 in the biogenesis of a lysosome-related fat storage organelle.

Caenorhabditis elegans gut granules are intestine specific lysosome-related organelles with birefringent and autofluorescent contents. We identified pgp-2, which encodes an ABC transporter, in screens for genes required for the proper formation of gut granules. pgp-2(-) embryos mislocalize birefringent material into the intestinal lumen and are lacking in acidified intestinal V-ATPase-containing compartments. Adults without pgp-2(+) function similarly lack organelles with gut granule characteristics. These cellular phenotypes indicate that pgp-2(-) animals are defective in gut granule biogenesis. Double mutant analysis suggests that pgp-2(+) functions in parallel with the AP-3 adaptor complex during gut granule formation. We find that pgp-2 is expressed in the intestine where it functions in gut granule biogenesis and that PGP-2 localizes to the gut granule membrane. These results support a direct role of an ABC transporter in regulating lysosome biogenesis. Previously, pgp-2(+) activity has been shown to be necessary for the accumulation of Nile Red-stained fat in C. elegans. We show that gut granules are sites of fat storage in C. elegans embryos and adults. Notably, levels of triacylglycerides are relatively normal in animals defective in the formation of gut granules. Our results provide an explanation for the loss of Nile Red-stained fat in pgp-2(-) animals as well as insight into the specialized function of this lysosome-related organelle.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

Components and dynamics of fiber formation define a ubiquitous biogenesis pathway for bacterial pili.

Type IV pili (Tfp) are a unique class of multifunctional surface organelles in Gram-negative bacteria, which play important roles in prokaryotic cell biology. Although components of the Tfp biogenesis machinery have been characterized, it is not clear how they function or interact. Using Neisseria gonorrhoeae as a model system, we report here that organelle biogenesis can be resolved into two discrete steps: fiber formation and translocation of the fiber to the cell surface. This conclusion is based on the capturing of an intermediate state in which the organelle is retained within the cell owing to the simultaneous absence of the secretin family member and biogenesis component PilQ and the twitching motility/pilus retraction protein PilT. This finding is the first demonstration of a specific translocation defect associated with loss of secretin function, and additionally confirms the role of PilT as a conditional antagonist of stable pilus fiber formation. These findings have important implications for Tfp structure and function and are pertinent to other membrane translocation systems that utilize a highly related set of components.

Adenosine Triphosphatases↗
PubMed2002

Oncostatin M regulates membrane traffic and stimulates bile canalicular membrane biogenesis in HepG2 cells.

Hepatocytes are the major epithelial cells of the liver and they display membrane polarity: the sinusoidal membrane representing the basolateral surface, while the bile canalicular membrane is typical of the apical membrane. In polarized HepG2 cells an endosomal organelle, SAC, fulfills a prominent role in the biogenesis of the canalicular membrane, reflected by its ability to sort and redistribute apical and basolateral sphingolipids. Here we show that SAC appears to be a crucial target for a cytokine-induced signal transduction pathway, which stimulates membrane transport exiting from this compartment promoting apical membrane biogenesis. Thus, oncostatin M, an IL-6-type cytokine, stimulates membrane polarity development in HepG2 cells via the gp130 receptor unit, which activates a protein kinase A-dependent and sphingomyelin-marked membrane transport pathway from SAC to the apical membrane. To exert its signal transducing function, gp130 is recruited into detergent-resistant membrane microdomains at the basolateral membrane. These data provide a clue for a molecular mechanism that couples the biogenesis of an apical plasma membrane domain to the regulation of intracellular transport in response to an extracellular, basolaterally localized stimulus.

Antigens, CD↗
PubMed2003

The G1 cyclin Cln3p controls vacuolar biogenesis in Saccharomyces cerevisiae.

How organelle biogenesis and inheritance is linked to cell division is poorly understood. In the budding yeast Saccharomyces cerevisiae the G(1) cyclins Cln1,2,3p control initiation of cell division. Here we show that Cln3p controls vacuolar (lysosomal) biogenesis and segregation. First, loss of Cln3p, but not Cln1p or Cln2p, resulted in vacuolar fragmentation. Although the vacuoles of cln3delta cells were fragmented, together they occupied a large space, which accounted for a significant fraction of the overall cell size increase in cln3delta cells. Second, cytosol prepared from cells lacking Cln3p had reduced vacuolar homotypic fusion activity in cell-free assays. Third, vacuolar segregation was perturbed in cln3delta cells. Our findings reveal a novel role for a eukaryotic G(1) cyclin in cytoplasmic organelle biogenesis and segregation.

Cell Cycle↗
PubMed1995

Disorders of peroxisome biogenesis.

The peroxisome is a ubiquitous, subcellular organelle containing more than 50 matrix enzymes that participate in a diverse array of metabolic pathways. Failure to assemble normal peroxisomes is the cellular hallmark of Zellweger syndrome and other human disorders of peroxisome biogenesis. Identification of the genes required for peroxisome biogenesis is proceeding at a rapid pace helped immeasurably by work in other species, particularly various yeasts. The ultimate goals of this effort are to identify all of these genes and to understand how their protein products interact to produce normal appearing and functioning peroxisomes. Attainment of these goals will lead to a better understanding of the peroxisome biogenesis disorders, their pathophysiology and treatment.

Animals↗
PubMed2006

Plastid biogenesis, between light and shadows.

Plastids are cellular organelles which originated when a photosynthetic prokaryote was engulfed by the eukaryotic ancestor of green and red algae and land plants. Plastids have diversified in plants from their original function as chloroplasts to fulfil a variety of other roles in metabolite biosynthesis and in storage, or purely to facilitate their own transmission, according to the cell type that harbours them. Therefore cellular development and plastid biogenesis pathways must be closely intertwined. Cell biological, biochemical, and genetic approaches have generated a large body of knowledge on a variety of plastid biogenesis processes. A brief overview of the components and functions of the plastid genetic machinery, the plastid division apparatus, and protein import to and targeting inside the organelle is presented here. However, key areas in which our knowledge is still surprisingly limited remain, and these are also discussed. Chloroplast-defective mutants suggest that a substantial number of important plastid biogenesis proteins are still unknown. Very little is known about how different plastid types differentiate, or about what mechanisms co-ordinate cell growth with plastid growth and division, in order to achieve what is, in photosynthetic cells, a largely constant cellular plastid complement. Further, it seems likely that major, separate plastid and chloroplast 'master switches' exist, as indicated by the co-ordinated gene expression of plastid or chloroplast-specific proteins. Recent insights into each of these developing areas are reviewed. Ultimately, this information should allow us to gain a systems-level understanding of the plastid-related elements of the networks of plant cellular development.

Biological Evolution↗
PubMed2004

CsdA, a cold-shock RNA helicase from Escherichia coli, is involved in the biogenesis of 50S ribosomal subunit.

CsdA, a DEAD-box protein from Escherichia coli, has been proposed to participate in a variety of processes, such as translation initiation, gene regulation after cold-shock, mRNA decay and biogenesis of the small ribosomal subunit. Whether the protein really plays a direct role in these multiple processes is however, not clear. Here, we show that CsdA is involved in the biogenesis of the large rather than the small ribosomal subunit. Deletion of the csdA gene leads to a deficit in free 50S subunits at low temperatures and to the accumulation of a new particle sedimenting around 40S. Analysis of the RNA and protein contents of this particle indicates that it corresponds to a mis-assembled large subunit. Sucrose gradient fractionation shows that in wild-type cells CsdA associates mainly with a pre50S particle. Presumably the RNA helicase activity of CsdA permits a structural rearrangement during 50S biogenesis at low temperature. We showed previously that SrmB, another DEAD-box RNA helicase, is also involved in 50S assembly in E.coli. Our results suggest that CsdA is required at a later step than SrmB. However, over-expression of CsdA corrects the ribosome defect of the srmB-deleted strain, indicating that some functional overlap exists between the two proteins.

Cold Temperature↗
PubMed2026

Single-nucleus profiling of postmortem diffuse midline gliomas identifies mitochondrial biogenesis as a resistance mechanism to imipridone therapy.

BACKGROUND: Imipridone ONC201 is the first FDA-approved therapy for H3K27-altered diffuse midline glioma; however, clinical responses remain limited. Defining tumor-intrinsic determinants and microenvironmental, extrinsic factors that shape sensitivity or resistance to imipridones will identify actionable therapeutic opportunities and inform improved clinical strategies. METHODS: To identify mechanisms of imipridone resistance, we obtained postmortem brain tissue from DMG patients who had received imipridones and/or standard care. Single-nucleus RNA and open-chromatin sequencing were performed on N = 22 cases. Immunofluorescence-based myeloid phenotyping was performed on N = 46 cases. Mitochondrial copy-number analysis was performed on N = 19 cases. Validation of imipridone sensitivity, its effect on mitochondrial density, and its synergy with inhibition of mitochondrial biogenesis were assessed in DMG primary cells. RESULTS: We established a single-cell RNA/open-chromatin atlas from postmortem DMG cases and found imipridone treatment resulting in regressed mesenchymal transition, reduced myeloid-derived suppressive cells, and reversed aberrant H3K27-altered enhancer activity. Resistant tumors showed increased mitochondrial density, turnover, and membrane potential. Mitochondrial biogenesis and PPARGC1A emerged as resistance biomarkers and actionable targets. CONCLUSIONS: These studies implicate mitochondrial biogenesis as a biomarker of imipridone resistance and a focus for the development of combinatorial strategies to provide effective therapeutic options for a challenging pediatric brain tumor.

Humans↗
PubMed2002

Dual roles of photosynthetic electron transport in photosystem I biogenesis: light induction of mRNAs and chromatic regulation at post-mRNA level.

Light regulation of photosystem I (PSI) biogenesis was studied in a unicellular green alga, Chlamydomonas reinhardtii. When Chlamydomonas cells were transferred from darkness to the light, mRNAs for both nuclear- and chloroplast-encoded PSI subunits were induced in concert. This light induction was inhibited by photosynthetic electron transport (PET) inhibitors, 3-(3,4 dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6 isopropyl-p-benzoquinone, but not by an uncoupler, carbonyl cyanide m-chlorophenylhydrazone. This indicated that PET plays a pivotal role in the light induction of PSI subunit mRNAs, but that photophosphorylation is not necessary. When we irradiated the Chlamydomonas cells with PSI-light (695 nm) or PSII-light (644 nm), which makes the plastoquinone pool oxidative and reductive, respectively, PSII-light caused the accumulation of PSI proteins more abundantly than did PSI-light. However, there was no difference for the PSI subunit mRNA levels between these light sources. From these results, we conclude that PET plays dual roles in the regulation of PSI biogenesis in Chlamydomonas: when cells are illuminated, PET first induces the PSI subunit mRNAs irrespective of the redox state of the intersystem electron carriers, and then their redox state fine-tunes PSI biogenesis at translational and/or post-translational steps to fulfil the chromatic adaptation.

Animals↗
PubMed2005

The Arabidopsis PEX12 gene is required for peroxisome biogenesis and is essential for development.

Peroxisomes perform diverse and vital functions in eukaryotes, and abnormalities in peroxisomal function lead to severe developmental disorders in humans. Peroxisomes are also involved in a wide array of physiological and metabolic functions unique to plants, yet many aspects of this important organelle are poorly understood. In yeast and mammals, various steps in peroxisome biogenesis require the function of peroxin (PEX) proteins, among which PEX12 is a RING finger peroxisomal membrane protein involved in the import of matrix proteins. To investigate the role of PEX12 in plants, we identified a T-DNA knockout allele of PEX12 and generated partial loss-of-function pex12 mutants using RNA interference. We show that pex12 null mutants are developmentally arrested during early embryogenesis, and that the embryo-lethal phenotype can be rescued by overexpression of the PEX12-cyan fluorescent protein fusion protein, which targets to the peroxisome. Using virus-induced gene-silencing techniques, we demonstrate that peroxisomal number and fluorescence of the yellow fluorescent protein-peroxisome targeting signal type 1 protein are greatly reduced when PEX12 is silenced. RNA interference plants with partial reduction of the PEX12 transcript exhibit impaired peroxisome biogenesis and function, inhibition of plant growth, and reduced fertility. Our work provides evidence that the Arabidopsis (Arabidopsis thaliana) PEX12 protein is required for peroxisome biogenesis and plays an essential role throughout plant development.

Amino Acid Sequence↗
PubMed2005

Coordination of nuclear and mitochondrial genome expression during mitochondrial biogenesis in Arabidopsis.

Mitochondrial biogenesis and function require the regulated and coordinated expression of nuclear and mitochondrial genomes throughout plant development and in response to cellular and environmental signals. To investigate the levels at which the expression of nuclear and mitochondrially encoded proteins is coordinated, we established an Arabidopsis thaliana cell culture system to modulate mitochondrial biogenesis in response to sugar starvation and refeeding. Sucrose deprivation led to structural changes in mitochondria, a decrease in mitochondrial volume, and a reduction in the rate of cellular respiration. All these changes could be reversed by the readdition of sucrose. Analysis of the relative mRNA transcript abundance of genes encoding nuclear and mitochondrially encoded proteins revealed that there was no coordination of expression of the two genomes at the transcript level. An analysis of changes in abundance and assembly of nuclear-encoded and mitochondrially encoded subunits of complexes I to V of the mitochondrial inner membrane in organello protein synthesis and competence for protein import by isolated mitochondria suggested that coordination occurs at the level of protein-complex assembly. These results further suggest that expression of the mitochondrial genome is insensitive to the stress imposed by sugar starvation and that mitochondrial biogenesis is regulated by changes in nuclear gene expression and coordinated at the posttranslational level.

Arabidopsis↗
PubMed1996

Fimbrial biogenesis genes of Pseudomonas aeruginosa: pilW and pilX increase the similarity of type 4 fimbriae to the GSP protein-secretion systems and pilY1 encodes a gonococcal PilC homologue.

Type 4 fimbriae of Pseudomonas aeruginosa are surface filaments involved in host colonization. They mediate both attachment to host epithelial cells and flagelia-independent twitching motility. Four additional genes, pilW, pilX, pilY1 and pilY2, are located on Spel fragment E in the 5 kb intergenic region between the previously characterized genes pilV and pilE, which encode prepilin-like proteins involved in type 4 fimbrial biogenesis. The phenotypes of a transposon insertion and other mutations constructed by allelic exchange show that these genes are involved in the assembly of type 4 fimbriae. The PilW and PilX proteins are membrane located, possess the hydrophobic N-terminus characteristic of prepilin-like proteins, and appear to belong to the GspJ and GspK group of proteins that are required for protein secretion in a wide range of Gram-negative bacteria. These findings increase the similarities between the fimbrial biogenesis and the Gsp-based protein-secretion supersystems. PilY1 is a large protein with C-terminal homology to the PilC2 protein of Neisseria gonorrhoeae, thought to be a fimbrial tip-associated adhesin, and which, like PilY1, is involved in fimbrial assembly. PilY1 appears to be located in both the membrane and the external fimbrial fractions. PilY2 is a small protein that appears to play a subtle role in fimbrial biogenesis and represents a new class of protein.

Alleles↗
PubMed2006

Analysis of the requirements for pilus biogenesis at the outer membrane usher and the function of the usher C-terminus.

Uropathogenic strains of Escherichia coli assemble type 1 and P pili to colonize the bladder and kidney respectively. These pili are prototype structures assembled by the chaperone/usher secretion pathway. In this pathway, a periplasmic chaperone works together with an outer membrane (OM) usher to control the folding of pilus subunits, their assembly into a pilus fibre and secretion of the fibre to the cell surface. The usher serves as the assembly and secretion platform in the OM. The usher has distinct functional domains, with the N-terminus providing the initial targeting site for chaperone-subunit complexes and the C-terminus required for subsequent stages of pilus biogenesis. In this study, we investigated the molecular interactions occurring at the usher during pilus biogenesis and the function of the usher C-terminus. We provide genetic and biochemical evidence that the usher functions as a complex in the OM and that interaction of the pilus adhesin with the usher is critical to prime the usher for pilus biogenesis. Analysis of C-terminal truncation and substitution mutants of the P pilus usher PapC demonstrated that the C-terminus is required for proper binding of chaperone-subunit complexes to the usher and plays an important role in assembly of complete pili.

Adhesins, Escherichia coli↗