title: Shear stress induces cell apoptosis via a c-Src-phospholipase D-mTOR signaling pathway in cultured podocytes.
abstract: The glomerular capillary wall, composed of endothelial cells, the glomerular basement membrane and the podocytes, is continually subjected to hemodynamic force arising from tractional stress due to blood pressure and shear stress due to blood flow. Exposure of glomeruli to abnormal hemodynamic force such as hyperfiltration is associated with glomerular injury and progressive renal disease, and the conversion of mechanical stimuli to chemical signals in the regulation of the process is poorly understood in podocytes. By examining DNA fragmentation, apoptotic nuclear changes and cytochrome c release, we found that shear stress induced cell apoptosis in cultured podocytes. Meanwhile, podocytes exposed to shear stress also stimulated c-Src phosphorylation, phospholipase D (PLD) activation and mammalian target of rapamycin (mTOR) signaling. Using the antibodies against c-Src, PLD(1), and PLD(2) to perform reciprocal co-immunoprecipitations and in vitro PLD activity assay, our data indicated that c-Src interacted with and activated PLD(1) but not PLD(2). The inhibition of shear stress-induced c-Src phosphorylation by PP(2) (a specific inhibitor of c-Src kinase) resulted in reduced PLD activity. Phosphatidic acid, produced by shear stress-induced PLD activation, stimulated mTOR signaling, and caused podocyte hypertrophy and apoptosis.
authors.affiliation: Louis Stokes Cleveland Veteran Affairs Medical Center, Case Western Reserve University, USA. chunfa.huang@case.edu
authors.forename: Chunfa
authors.initials: C
authors.lastname: Huang
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Bruggeman
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Hydo
authors.forename: R Tyler
authors.initials: RT
authors.lastname: Miller
mesh_terms: D000818:Animals; D017209:Apoptosis; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D051379:Mice; D010713:Phosphatidylcholines / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D010766:Phosphorylation; D050199:Podocytes / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D033081:Shear Strength; D015398:Signal Transduction; D013312:Stress, Physiological; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D019061:src-Family Kinases
chemical_list: C412373:AG 1879; D010713:Phosphatidylcholines; D011743:Pyrimidines; C546843:mTOR protein, mouse; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D058570:TOR Serine-Threonine Kinases; D010739:Phospholipase D