HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 296/5/C1151    most recent 00343.2008v2 00343.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Atkins, K. B. Articles by Brosius, F. C. Search for Related Content PubMed PubMed Citation Articles by Atkins, K. B. Articles by Brosius, F. C., 3rd.

VASCULAR BIOLOGY

A rapid, PPAR--dependent effect of pioglitazone on the phosphorylation of MYPT

Departments of ¹Internal Medicine and ²Physiology, University of Michigan Medical School, Ann Arbor, Michigan

Submitted 2 July 2008 ; accepted in final form 24 February 2009

Peroxisome proliferator-activated receptor (PPAR)- ligands, thiazolidinediones, have been demonstrated to regulate vascular reactivity. We examined the effect of pioglitazone (PIO; 20 µM) in rat primary cultured aortic smooth muscle cells on constitutive phosphorylation of the regulatory subunit of myosin phosphatase (MYPT). PIO decreased the phosphorylation of Thr⁶⁹⁷ on MYPT within 15 min, and the inhibition was maintained up to 6 h. The PPAR- antagonist GW-9662 (5 µM) abrogated the inhibition of Thr⁶⁹⁷ phosphorylation mediated by PIO. Because longer-term PIO treatment inhibits RhoA/Rho kinase (ROCK) signaling and Thr⁶⁹⁷ phosphorylation, we tested the effect of the ROCK inhibitor Y-27632 (10 µM) on the inhibition of Thr⁶⁹⁷ phosphorylation by PIO. Y-27632 alone inhibited Thr⁶⁹⁷ phosphorylation, and there was an additive effect with PIO. In addition, up to 1 h of PIO treatment did not affect RhoA localization or decrease ROCK-dependent phosphorylation of Thr⁸⁵⁵. These results suggest that the effect of PIO is independent of inhibition of RhoA/ROCK. PIO increased the phosphorylation of Ser⁶⁹⁶ in the same time course as its effect on Thr⁶⁹⁷. Ser⁶⁹⁶ has been shown to be phosphorylated by PKA and PKG. PKA inhibitor H-89 (10 µM) and PKG inhibitor KT-5823 (0.5 µM) abrogated the effect of PIO on both Thr⁶⁹⁷ and Ser⁶⁹⁶ phosphorylation. The constitutive turnover of phosphorylation of Thr⁶⁹⁷ is rapid, suggesting that the decreased phosphorylation of Thr⁶⁹⁷ by PIO is due to enhanced phosphorylation of Ser⁶⁹⁶. This is supported by the finding that PIO blocks ANG II-stimulated phosphorylation of Thr⁶⁹⁷ but not ANG II-stimulated RhoA translocation. Therefore, the effect of shorter-term PIO apparently is to increase myosin light chain phosphatase activity, thereby desensitizing the vascular smooth muscle to agonist signaling.

myosin phosphatase regulatory subunit; peroxisome proliferator-activated receptor-; vascular