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PubMed2003

A role for VASP in RhoA-Diaphanous signalling to actin dynamics and SRF activity.

Vasodilator-stimulated phosphoprotein (VASP) is involved in multiple actin-mediated processes, including regulation of serum response factor (SRF) activity. We used the SRF transcriptional assay to define functional domains in VASP and to show that they coincide with those required for F-actin accumulation, as determined by a quantitative FACS assay. We identified inactive VASP mutants that can interfere both with F-actin assembly and with SRF activation by wild-type VASP. These VASP mutants also inhibit actin-based motility of Vaccinia virus and Shigella flexneri. VASP-induced F-actin accumulation and SRF activation require both functional Rho and its effector mDia, and conversely, mDia-mediated SRF activation is critically dependent on functional VASP. VASP and mDia also associate physically in vivo. These findings show that VASP and mDia function cooperatively downstream of Rho to control F-actin assembly and SRF activity.

3T3 Cells↗

PubMed1976

[Purification of skin reactive factor (SRF) in mice].

For the purification and further characterisation of the skin-reactive factor (SRF) of the mouse, the SRF-containing ascitic fluid of Ehrlich ascites tumor was exposed to different separation or elution procedures. After preliminary purification by (NH4)2SO4 precipitation when the total activity was not in the dialysable supernatant, gel-chromatographic separation (Sephadex G-200), immune electrophoretic investigations as well as ion exchange chromatography were performed. The skin-reactive activity in fraction I of gel chromatiography is presumably caused by a toxic substance with skin-irritating properties. The SRF demonstrable in fraction II/2 has a molecular weight similar to that of albumin, can be found in the ion exchange chromatography (DEAE-Sephadex A-50-column) in fraction III, and is of proteinic nature.

Animals↗

PubMed1976

Depolarization-induced calcium release from sarcoplasmic reticulum fragments. II. Release of calcium incorporated with ATP.

Ca2& incorporated in vesicles of sarcoplasmic reticulum fragments (SRF) by diffusion could be released rapidly by changing the ionic environment, by dilution from methanesulfonate (MS) to chloride. This ion exchange is considered to make the membrane potential of SRF inside-negative. Much faster release of Ca2t was also observed upon osmotic change from high to low. These responses were very similar to the Ca2& release from SRF after take up using ATP, but the release rate was slow in the case of anion exchnage. The behavior of K&, Na&, sucrose, and inulin incorporated in SRF was followed upon similar treatment. These ions and nolecules were not released upon ion exchange, but were immediately released by osomtic treatment. Therefore, the Ca& release upon anion exchange was not due to the bursting of SRF, but to a direct effect such as a membrane potential change of the SRF. The behavior of anion such as C1- and propionate could not followed by the same method because of the large permability of these anions. It was also shown that Ca& release upon ion exchange was not a direct effect of pH change. Liver microsomes did not show Ca& release upon the same treatment as SRF.

Adenosine Triphosphate↗

PubMed2026

Associations of Illness Perception, Resignation Coping, and Social Support With Self-Regulatory Fatigue in Patients With Type 2 Diabetes: A Cross-Sectional Study.

AIMS: To examine the associations among illness perception, resignation coping, social support, and self-regulatory fatigue (SRF) in patients with Type 2 diabetes mellitus. The study specifically explores whether resignation coping and social support exhibit indirect associations with SRF in the context of illness perception. DESIGN: A cross-sectional study. METHODS: From November 2024 to October 2025, a convenience sample of 302 adult patients with T2DM was recruited from a tertiary general hospital in China. Participants completed validated instruments with established psychometric properties, namely the Brief Illness Perception Questionnaire, the Medical Coping Modes Questionnaire, the Perceived Social Support Scale, and the Self-Regulatory Fatigue Scale. Statistical analyses included Spearman correlation and serial mediation analysis using the PROCESS Macro (Model 6) with bias-corrected bootstrapping. RESULTS: SRF was positively correlated with negative illness perception (r = 0.579, p < 0.01) and resignation coping (r = 0.612, p < 0.01), and negatively correlated with social support (r = -0.598, p < 0.01). Serial mediation analysis revealed that illness perception was associated with SRF through indirect pathways involving resignation coping and social support. Resignation coping and social support mediated the association between illness perception and self-regulatory fatigue, both individually and sequentially. CONCLUSIONS: Negative illness perception correlates with higher SRF. This observed correlation is additionally linked to indirect pathways involving resignation coping and lower social support. Collectively, these findings highlight a pattern of interrelated cognitive (illness perception), behavioural (resignation coping), and resource (social support) factors that are associated with self-regulatory fatigue in this cross-sectional study. IMPLICATIONS FOR THE PROFESSION: The findings offer a clear, evidence-based framework for nursing practice. They highlight the potential value of integrated assessment and intervention that simultaneously addresses patients' illness beliefs, maladaptive coping strategies, and social support systems, which are associated with lower SRF and better diabetes self-management. REPORTING METHOD: This study adheres to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for cross-sectional studies. PATIENT OR PUBLIC CONTRIBUTION: Patients participated solely as research participants by providing survey data. They were not involved in the study design, implementation, data analysis, interpretation, or manuscript preparation. All patients provided written informed consent prior to questionnaire completion.

Humans↗

PubMed1979

Protein synthesis in rabbit reticulocytes: characteristics of a postribosomal supernatant factor that reverses inhibition of protein synthesis in heme-deficient lysates and inhibition of ternary complex (Met-tRNAfMet.eIF-2.GTP) formation by heme-regulated inhibitor.

During heme deficiency in reticulocyte lysates, a translational inhibitor (heme-regulated inhibitor, HRI) that blocks polypeptide chain initiation is activated. HRI is a protein kinase that specifically phosphorylates the 38,000-dalton subunit of the Met-tRNAfMet binding factor, eIF-2. Phosphorylation of eIF-2 by HRI prevents its interaction with at least two additional factors, resulting in a net reduction in formation of ternary complex (Met-tRNAfMet.eIF-2.GTP) and AUG-dependent transfer of Met-tRNAfMet to 40S ribosomal subunits. A factor (sRF) that reverses protein synthesis inhibition in heme-deficient lysates has been purified from reticulocyte postribosomal supernatant. sRF also reverses the inhibition of ternary complex formation by HRI in a fractionated system. The ternary complex inhibition reversal activity and the protein synthesis inhibition reversal activity cosediment at 12.5 S upon glycerol density gradient centrifugation, and both activities are sensitive to heat or N-ethylmaleimide. Purified sRF does not dephosphorylate eIF-2 whose phosphorylation has been catalyzed by HRI, nor does the sRF prevent the phosphorylation of eIF-2 by HRI in a fractionated system. sRF stimulates ternary complex formation by both phosphorylated and nonphosphorylated eIF-2. These observations suggest that the sensitivity of protein synthesis to phosphorylation of eIF-2 by HRI may be modulated by the concentration and activity of sRF.

Animals↗

PubMed1978

The effects of storage of sarcoplasmic reticulum fragments on the Ca2+, Mg2+-ATPase.

The effects of K+ and Na+ on the Ca2+,Mg2+-ATPase of sarcoplasmic reticulum fragments (SRF) were investigated at 1 mM ATP. There was an alteration of the sensitivity of the ATPase to the monovalent cations during storage of the SRF preparation. The Ca2+, Mg2+-ATPase of freshly prepared SRF was slightly activated by 5-10 mM K+ and Na+. Mg2+-ATPase was inhibited by both the monovalent cations to the same extent, and this response to the ions was independent of the freshness of the preparations. After storage of SRF, however, the Ca2+,Mg2+-ATPase was markedly activated by higher concentrations of K+ and Na+ (0.2-0.3 M). K+ and Na+ reduced the Ca uptake at the steady state in freshly prepared SRF, but did not affect pre-steady state uptake. In the presence of oxalate, the rate of Ca accumulation both in fresh and stored preparations was activated by 0.1-0.2 M K+ and Na+. The Ca2+, mg2+-ATPase with oxalate, so-called "extra ATPase," showed the same response to the ions as did the activity without oxalate during storage.

Adenosine Triphosphatases↗

PubMed2004

Ternary complex factor-serum response factor complex-regulated gene activity is required for cellular proliferation and inhibition of apoptotic cell death.

Members of the ternary complex factor (TCF) subfamily of the ETS-domain transcription factors are activated through phosphorylation by mitogen-activated protein kinases (MAPKs) in response to a variety of mitogenic and stress stimuli. The TCFs bind and activate serum response elements (SREs) in the promoters of target genes in a ternary complex with a second transcription factor, serum response factor (SRF). The association of TCFs with SREs within immediate-early gene promoters is suggestive of a role for the ternary TCF-SRF complex in promoting cell cycle entry and proliferation in response to mitogenic signaling. Here we have investigated the downstream gene regulatory and phenotypic effects of inhibiting the activity of genes regulated by TCFs by expressing a dominantly acting repressive form of the TCF, Elk-1. Inhibition of ternary complex activity leads to the downregulation of several immediate-early genes. Furthermore, blocking TCF-mediated gene expression leads to growth arrest and triggers apoptosis. By using mutant Elk-1 alleles, we demonstrated that these effects are via an SRF-dependent mechanism. The antiapoptotic gene Mcl-1 is identified as a key target for the TCF-SRF complex in this system. Thus, our data confirm a role for TCF-SRF-regulated gene activity in regulating proliferation and provide further evidence to indicate a role in protecting cells from apoptotic cell death.

Alleles↗

PubMed1976

Depolarization-induced calcium release from sarcoplasmic reticulum fragments. I. Release of calcium taken up upon using ATP.

Ca2& taken up by sarcoplasmic reticulum membrane fragments (SRF) upon using ATP could be released rapidly by changing the anion outside the vesicles from methanesulfonate to chloride. It is considered that this anion exchange caused depolarization of the sarcoplasmic reticulum membrane. Similar rapid release of Ca2& taken up by SRF was also caused by a change from high to low osmotic pressure, probably due to bursting of the membrane. On the basis of experiments in which these two types of Ca2& release were discriminated, it was concluded that Ca2& bound inside the membrane was released directly by anion exchange (depolarization). However, Ca2& release was not caused by cation exchange. Sucrose inhibited these two types of Ca2& release. Cia2& taken up in the presence of oxalate could not be released by any treatment used. Liver microsome fraction also has Ca2& uptake activity. However, Ca2& was not released upon anion exchange, but was released upon oxmotic change. These results show that Ca2& release from SRF upon anion exchange is specific to the sarcoplasmic reticulum membrane. In conclusion, SRF membrane retains the ability to respond to the depolarization caused by ion exchange and can release the accumulated Ca2&.

Adenosine Triphosphate↗

PubMed1979

Identification of iron-sulfur centers in the iron-molybdenum proteins of nitrogenase.

The core extrusion method has been applied to the determination of the type ([2Fe-2S], [4Fe-4S]) and number of iron-sulfur centers in the FeMo proteins of the nitrogenases from Clostridium pasteurianum and Azotobacter vinelandii. The method involves extrusion with o-xylyl-alpha, alpha'-dithiol, ligand exchange of the extrusion products with p-CF3C6H4SH (RFSH), and identification and quantitation of the resultant [FenSn(SRF)4]2- complexes (n = 2,4) by 19F NMR spectroscopy. In hexamethylphosphoramide/water, 4:1 (vol/vol), 49-56% of the Fe content was extruded as [Fe4S4(SRF)4]2-, corresponding to 3,4-4.0 Fe4S4 cores per alpha 2 beta 2 subunit complex. The extruded iron does not arise from the FeMo cofactor, separate examination of which detected no extrusion products, and corresponds to 90-103% of noncofactor iron. No significant quantity of Fe2S2 cores was extruded. These results indicate the presence of four [4Fe-4S] centers per alpha 2 beta 2 subunit complex in preparations undepleted in iron. There are two main structural populations of iron atoms in these proteins, those in the cubane-type Fe4S4 cores and those in the FeMo cofactor.

Azotobacter↗

PubMed1979

Characterization of the iron-sulfur centers in succinate dehydrogenase.

Two techniques have been applied to the determination of the number and type (2-Fe, 4-Fe) of iron-sulfur centers in the iron-sulfur flavoprotein succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1]. One procedure uses p-CF3C6H4SH as an extrusion reagent and Fourier transform 19F nuclear magentic resonance as the method of detection and quantitation of extruded cores of these centers in the form of [Fe2S2(SRF)4]2- and [Fe4S4(SRF)4]2- (RF = p-C6H4CF3). The second procedure, interprotein core transfer, involves thiol displacement of iron-sulfur cores followed by specific core transfer to the apoproteins of Bacillus polymyxa ferredoxin and adrenodoxin. Detection and quantitation are accomplished by electron paramagnetic resonance of reduced proteins at low temperatures. Both procedures clearly show that succinate dehydrogenase contains two dimeric (Fe2S2) and one tetrameric (Fe4S4) centers per mole of histidyl flavin, accounting for all eight nonheme iron and eight labile sulfur atoms found by chemical analysis. These results remove uncertainties created by the less than stoichiometric amounts of binuclear centers detected by electron paramagnetic resonance after dithionite reduction and provide secure characterization of the iron-sulfur centers in this enzyme.

Electron Spin Resonance Spectroscopy↗

PubMed2026

Emerging Molecularly Defined Bone and Soft Tissue Diagnoses: When Do They Matter?

With the rapid advancement of molecular pathology and the explosion of genomic data, our understanding of neoplasms continues to evolve. In this review, we introduce 3 recently classified mesenchymal neoplasms, the categorization of which was refined based on their underlying molecular genetic profiles. These entities were recently highlighted by the senior author at the United States and Canadian Academy of Pathology Long Course. To underscore the importance of their proper recognition, this review was prepared to reach a broader audience. Recognition of these tumors is particularly important because their mimickers often have markedly disparate prognoses and management strategies, making accurate diagnosis critical. The 3 entities discussed in this study are the following: (1) SRF-rearranged myoid neoplasms (formerly cellular myofibroma), (2) superficial CD34-positive fibroblastic tumors, and (3) kinase-altered spindle cell neoplasms. This review aimed to highlight the key clinicopathologic features of these tumors to facilitate accurate diagnosis, discuss ancillary studies that assist in navigating the differential diagnoses, and outline strategies to avoid common diagnostic pitfalls. Finally, we emphasize when molecular characterization may be necessary to guide diagnosis and support appropriate clinical management.

Humans↗