Phorbol esters increase MLC phosphorylation and actin remodeling in bovine lung endothelium without increased contraction

Natalia V. Bogatcheva, Alexander D. Verin, Peiyi Wang, Anna A. Birukova, Konstantin G. Birukov, Tamara Mirzopoyazova, Djanybek M. Adyshev, Eddie T. Chiang, Michael T. Crow, Joe G.N. Garcia

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Direct protein kinase C (PKC) activation with phorbol myristate acetate (PMA) results in the loss of endothelial monolayer integrity in bovine lung endothelial cells (EC) but produces barrier enhancement in human lung endothelium. To extend these findings, we studied EC contractile events and observed a 40% increase in myosin light chain (MLC) phosphorylation in bovine endothelium following PMA challenge. The increase in PMA-mediated MLC phosphorylation occurred at sites distinct from Ser19/Thr18, sites catalyzed by MLC kinase (MLCK), and immunoblotting with antibodies specific to phosphorylated Ser19/Thr18 demonstrated profound time-dependent Ser19/Thr18 dephosphorylation. These events occurred in conjunction with rearrangement of stress fibers into a grid-like network, but without an increase in cellular contraction as measured by silicone membrane wrinkling assay. The PMA-induced MLC dephosphorylation was not due to kinase inhibition but, rather, correlated with rapid increases in myosin-associated phosphatase 1 (PPase 1) activity. These data suggest that PMA-mediated EC barrier regulation may involve dual mechanisms that alter MLC phosphorylation. The increase in bovine MLC phosphorylation likely occurs via direct PKC-dependent MLC phosphorylation in conjunction with decreases in Ser19/Thr19 phosphorylation catalyzed by MLCK due to PMA-induced increases in PPase 1 activity. Together, these events result in stress fiber destabilization and profound actin rearrangement in bovine endothelium, which may result in the physiological alterations observed in these models.

Original languageEnglish (US)
Pages (from-to)L415-L426
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number2 29-2
StatePublished - Aug 1 2003
Externally publishedYes


  • Myosin light chain kinase
  • Myosin phosphatase
  • Phorbol myristate acetate
  • Protein kinase C

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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