Phosphorylation of telokin by cyclic nucleotide kinases and the identification of in vivo phosphorylation sites in smooth muscle

AbstractThe Ca2+-independent acceleration of dephosphorylation of the regulatory light chain of smooth muscle myosin and relaxation of smooth muscle by telokin are enhanced by cyclic nucleotide-activated protein kinase(s) [Wu et al. (1998) J. Biol. Chem. 273, 11362–11369]. The purpose of this study was to determine the in vivo site(s) and in vitro rates of telokin phosphorylation and to evaluate the possible effects of sequential phosphorylation by different kinases. The in vivo site(s) of phosphorylation of telokin were determined in rabbit smooth muscles of longitudinal ileum and portal vein. Following stimulation of ileum with forskolin (20 μM) the serine at position 13 was the only amino acid to exhibit increased phosphorylation. Rabbit portal vein telokin was phosphorylated on both Ser-13 and -19 as a result of forskolin and GTPγS stimulation in vivo. Point mutation of Ser-13 (to Ala or Asp) abolished in vitro phosphorylation by cyclic nucleotide-dependent protein kinases

Losartan Decreases p42/44 MAPK Signaling and Preserves LZ+ MYPT1 Expression

Heart failure is associated with impairment in nitric oxide (NO) mediated vasodilatation, which has been demonstrated to result from a reduction in the relative expression of the leucine zipper positive (LZ+) isoform of the myosin targeting subunit (MYPT1) of myosin light chain phosphatase. Further, captopril preserves normal LZ+ MYPT1 expression, the sensitivity to cGMP-mediated vasodilatation and modulates the expression of genes in the p42/44 MAPK and p38 MAPK signaling cascades. This study tests whether angiotensin receptor blockade (ARB) with losartan decreases p42/44 MAPK or p38 MAPK signaling and preserves LZ+ MYPT1 expression in a rat infarct model of heart failure. In aortic smooth muscle, p42/44 MAPK activation increases and LZ+ MYPT1 expression falls after LAD ligation. Losartan treatment decreases the activation of p42/44 MAPK to the uninfarcted control level and preserves normal LZ+ MYPT1 expression. The expression and activation of p38 MAPK, however, is low and does not change following LAD ligation or with losartan therapy. These data suggest that either reducing or blocking the effects of circulating angiotensin II, both decreases the activation of the p42/44 MAPK signaling cascade and preserves LZ+ MYPT1 expression. Thus, the ability of ACE-inhibitors and ARBs to modulate the vascular phenotype, to preserve normal flow mediated vasodilatation may explain the beneficial effects of these drugs compared to other forms of afterload reduction in the treatment of heart failure

Actions of Calcium on Smooth Muscle a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72185/1/j.1749-6632.1988.tb33358.x.pd