guanosine-triphosphate and Fibrosis

Topics: Alternative Splicing; Aminoacyltransferases; Animals; Calcium; Carbon-Nitrogen Lyases; Cell Death; Cell Survival; Fibrosis; Gene Expression; GTP-Binding Proteins; Guanosine Triphosphate; Humans; Inflammation; Isoenzymes; Macrophages; Phagocytosis; Protein Disulfide-Isomerases; Protein Glutamine gamma Glutamyltransferase 2; Transglutaminases

Pleural mesothelial cells (PMCs) play a central role in the progression of pleural fibrosis. As pleural injury progresses to fibrosis, PMCs transition to mesenchymal myofibroblast via mesothelial mesenchymal transition (MesoMT), and produce extracellular matrix (ECM) proteins including collagen and fibronectin (FN1). FN1 plays an important role in ECM maturation and facilitates ECM-myofibroblast interaction, thus facilitating fibrosis. However, the mechanism of FN1 secretion is poorly understood. We report here that myosin 5b (Myo5b) plays a critical role in the transportation and secretion of FN1 from human pleural mesothelial cells (HPMCs). TGF-β significantly increased the expression and secretion of FN1 from HPMCs and facilitates the close association of Myo5B with FN1 and Rab11b. Moreover, Myo5b directly binds to GTP bound Rab11b (Rab11b-GTP) but not GDP bound Rab11b. Myo5b or Rab11b knockdown via siRNA significantly attenuated the secretion of FN1 without changing FN1 expression. TGF-β also induced Rab11b-GTP formation, and Rab11b-GTP but not Rab11b-GDP significantly activated the actin-activated ATPase activity of Myo5B. Live cell imaging revealed that Myo5b- and FN1-containing vesicles continuously moved together in a single direction. These results support that Myo5b and Rab11b play an important role in FN1 transportation and secretion from HPMCs, and consequently may contribute to the development of pleural fibrosis.

Topics: Fibronectins; Fibrosis; Guanosine Triphosphate; Humans; Myosin Heavy Chains; Myosin Type V; Myosins; Transforming Growth Factor beta

The Ras and Rho family of GTPases serve as essential molecular switches in the downstream signalling of many cytokines involved in the regulation of renal fibroblast activity. Prenylation is a post-translational process critical to the membrane localization and function of these GTPases. We studied the effects of a farnesyltransferase inhibitor BMS-191563 and geranylgeranyltransferase inhibitor GGTI-298 on renal fibrogenesis in vitro.. Functional studies examined the effects of BMS-191563 and GGTI-298 on rat renal fibroblast kinetics, collagen synthesis and collagen gel contraction. Pro-collagen alpha1(I) mRNA expression was measured by Northern analysis and CTGF expression by Western blotting.. Fibroblast proliferation was significantly reduced by both agents. Exposure of fibroblasts to BMS-191563 resulted in a significant reduction in total collagen production and pro-collagen alpha1(I) mRNA expression, an effect also observed but to a lesser degree with GGTI-298. Both agents significantly reduced CTGF protein expression. Fibroblast-mediated collagen I lattice contraction was decreased at 48 h by GGTI-298, an effect not observed with BMS-191563. Consistent with this finding, marked actin filament disassembly was evident by phalloidin staining of fibroblasts exposed to GGTI-298.. BMS-191563 and GGTI-298 exhibit different effects on renal fibroblast function reflecting their predominant roles in inhibiting prenylation of Ras or Rho proteins respectively. Further studies are warranted to establish their potential therapeutic application in the treatment of progressive renal disease.

Topics: Actin Cytoskeleton; Alkyl and Aryl Transferases; Animals; Apoptosis; Benzamides; Cell Proliferation; Collagen; Collagen Type I; Collagen Type I, alpha 1 Chain; Connective Tissue Growth Factor; Cytoskeleton; Enzyme Inhibitors; Farnesyltranstransferase; Fibroblasts; Fibrosis; Guanosine Triphosphate; Immediate-Early Proteins; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Kidney; Kinetics; Protein Prenylation; ras Proteins; Rats; RNA, Messenger; Time Factors

A case of erythropoietic protoporphyria (EPP) with severe acute abdominal pain and jaundice was reported. Erythrocyte protoporphyrin (PP) levels were constantly high, and liver histology showed a slight fibrosis with inflammatory infiltration. During the investigation period of 18 months, erythrocyte PP levels closely paralleled those of serum gamma-GTP.

Topics: Acute Disease; Adult; Biopsy; Erythrocytes; Erythropoiesis; Fibrosis; Guanosine Triphosphate; Humans; Liver Diseases; Male; Porphyrias; Porphyrins