Department of Cell Biology
Alternative Splicing; Amino Acid Sequence; Animals; Aorta; Blotting, Western; COS Cells; Calcium-Binding Proteins; DNA, Complementary; Enzyme Activation; Ferrets; Glutathione Transferase; Membrane Proteins; Microfilament Proteins; Microscopy, Fluorescence; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Models, Genetic; Molecular Sequence Data; Muscle, Smooth; Oligonucleotides, Antisense; Phosphorylation; Protein Binding; Protein Kinase C; Protein Structure, Tertiary; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Signal Transduction; Subcellular Fractions; Time Factors; Transfection; Two-Hybrid System Techniques
Cell Biology | Life Sciences | Medicine and Health Sciences
The mechanisms by which protein kinase C (PKC) and extracellular-signal-regulated kinases (ERK1/2) govern smooth-muscle contractility remain unclear. Calponin (CaP), an actin-binding protein and PKC substrate, mediates signaling through ERK1/2. We report here that CaP sequences containing the CaP homology (CH) domain bind to the C-terminal 251 amino acids of smooth-muscle archvillin (SmAV), a new splice variant of supervillin, which is a known actin- and myosin-II-binding protein. The CaP-SmAV interaction is demonstrated by reciprocal yeast two-hybrid and blot-overlay assays and by colocalization in COS-7 cells. In differentiated smooth muscle, endogenous SmAV and CaP co-fractionate and co-translocate to the cell cortex after stimulation by agonist. Antisense knockdown of SmAV in tissue inhibits both the activation of ERK1/2 and contractions stimulated by either agonist or PKC activation. This ERK1/2 signaling and contractile defect is similar to that observed in CaP knockdown experiments. In A7r5 smooth-muscle cells, PKC activation by phorbol esters induces the reorganization of endogenous, membrane-localized SmAV and microfilament-associated CaP into podosome-like structures that also contain F-actin, nonmuscle myosin IIB and ERK1/2. These results indicate that SmAV contributes to the regulation of contractility through a CaP-mediated signaling pathway, involving PKC activation and phosphorylation of ERK1/2.
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Citation: J Cell Sci. 2004 Oct 1;117(Pt 21):5043-57. Epub 2004 Sep 21. Link to article on publisher's site