Role of Rho and myosin phosphorylation in actin stress fiber assembly in mesangial cells

Jeffrey I. Kreisberg, Nandini Ghosh-Choudhury, Robert A. Radnik, Martin A. Schwartz

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Treatment of renal glomerular mesangial cells with adenosine 3',5'- cyclic monophosphate (cAMP)-elevating agents induces actin stress fiber disassembly, myosin light chain (MLC) dephosphorylation, loss of adhesion to the substratum and cell shape change [J. I. Kreisberg and M. A. Venkatachalam. Am. J. Physiol. 251 (Cell Physiol. 20): C505-C511, 1986]. Thrombin and vasopressin block the effects of cAMP. Because these agents are known to promote stress fiber formation via the small GTP-binding protein Rho, we investigated the effect of an activated variant of Rho on the response to cAMP elevation. Microinjecting V14-Rho completely blocked the effect of cAMP elevation on cell shape and the actin cytoskeleton, whereas inactivating Rho with botulinum C3 exoenzyme induced stress fiber disruption and cell retraction that was indistinguishable from that caused by elevations in intracellular levels of cAMP. Disruption of actin stress fibers by cAMP has previously been ascribed to MLC dephosphorylation; however, both C3 and cytochalasin D also caused dephosphorylation of MLC, whereas blocking MLC dephosphorylation failed to block the cAMP-induced loss of actin stress fibers. We conclude that Rho can modulate the effects of cAMP elevation and suggest that MLC dephosphorylation may be a consequence of actin stress fiber disassembly.

Original languageEnglish (US)
Pages (from-to)F283-F288
JournalAmerican Journal of Physiology - Renal Physiology
Issue number2 42-2
StatePublished - Aug 1997


  • Myosin light chain
  • Rho
  • Shape change

ASJC Scopus subject areas

  • Physiology
  • Urology


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