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1 Cardiovascular Research Group, University of Manchester, United Kingdom
2 School of Biological and Biomedical Sciences, University of Durham, United Kingdom
* To whom correspondence should be addressed. E-mail: vohanian{at}manchester.ac.uk.
Regulation of small artery contractility by vasoconstrictors is important for vascular function and actin cytoskeleton remodelling is required for contraction. p38MAPK and tyrosine kinases are implicated in actin polymerisation and contraction, through Hsp27 and the cytoskeletal protein paxillin respectively. We evaluated the roles of downstream targets of p38MAPK and tyrosine kinases in cytoskeletal reorganisation and contraction and whether the two signalling pathways regulate contraction independent of each other. We identified expression of the paxillin homologue Hic-5 and showed its activation by noradrenaline (NA) in a Src dependent manner. Furthermore, we demonstrated an NA induced interaction of PYK2 but not Src or p125FAK with Hic-5. This interaction was Src dependent suggesting that Hic-5 was a substrate for PYK2 downstream from Src. Activation of Hic-5 induced its relocalisation to the cytosol. Parallel activation of Hsp27 by NA was p38MAPK dependent and led to its dissociation from actin filaments, its translocation from membrane to cytosol and increased actin polymerisation. Both Hsp27 and Hic5 activation resulted in their association, within the same time frame as NA induced contraction and inhibition of either p38MAPK or Src inhibited the interaction between Hsp27 and Hic5 and the contractile response. Furthermore, combined p38MAPK and Src inhibition had no greater effect on contraction than individual inhibition, suggesting that the two pathways act through a common mechanism. These data show that NA induced activation and association of Hsp27 and Hic-5 is required for reorganisation of the actin cytoskeleton and force development in small arteries.
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