TY - JOUR
T1 - Phosphorylation of caldesmon by p21-activated kinase. Implications for the Ca2+ sensitivity of smooth muscle contraction
AU - Foster, D. Brian
AU - Shen, Li Hua
AU - Kelly, John
AU - Thibault, Pierre
AU - Van Eyk, Jennifer
AU - Mak, Alan S.
PY - 2000/1/21
Y1 - 2000/1/21
N2 - We have previously shown that p21-activated kinase, PAK, induces Ca2+- independent contraction of Triton-skinned smooth muscle with concomitant increase in phosphorylation of caldesmon and desmin but not myosin-regulatory light chain (Van Eyk, J. E., Arrell, D. K., Foster, D. B., Strauss, J. D., Heinonen, T. Y., Furmaniak-Kazmierczak, E., Cote, G. P., and Mak, A. S. (1998) J. Biol. Chem. 273, 23433-23439). In this study, we provide biochemical evidence implicating a role for PAK in Ca2+independent contraction of smooth muscle via phosphorylation of caldesmon. Mass spectroscopy data show that stoichiometric phosphorylation occurs at Ser657 and Ser687 abutting the calmodulin-binding sites A and B of chicken gizzard caldesmon, respectively. Phosphorylation of Ser657 and Ser687 has an important functional impact on caldesmon. PAK- phosphorylation reduces binding of caldesmon to calmodulin by about 10-fold whereas binding of calmodulin to caldesmon partially inhibits PAK phosphorylation. Phosphorylated caldesmon displays a modest reduction in affinity for actintropomyosin but is significantly less effective in inhibiting actin-activated S1 ATPase activity in the presence of tropomyosin. We conclude that PAK-phosphorylation of caldesmon at the calmodulin-binding sites modulates caldesmon inhibition of actin-myosin ATPase activity and may, in concert with the actions of Rho-kinase, contribute to the regulation of Ca2+ sensitivity of smooth muscle contraction.
AB - We have previously shown that p21-activated kinase, PAK, induces Ca2+- independent contraction of Triton-skinned smooth muscle with concomitant increase in phosphorylation of caldesmon and desmin but not myosin-regulatory light chain (Van Eyk, J. E., Arrell, D. K., Foster, D. B., Strauss, J. D., Heinonen, T. Y., Furmaniak-Kazmierczak, E., Cote, G. P., and Mak, A. S. (1998) J. Biol. Chem. 273, 23433-23439). In this study, we provide biochemical evidence implicating a role for PAK in Ca2+independent contraction of smooth muscle via phosphorylation of caldesmon. Mass spectroscopy data show that stoichiometric phosphorylation occurs at Ser657 and Ser687 abutting the calmodulin-binding sites A and B of chicken gizzard caldesmon, respectively. Phosphorylation of Ser657 and Ser687 has an important functional impact on caldesmon. PAK- phosphorylation reduces binding of caldesmon to calmodulin by about 10-fold whereas binding of calmodulin to caldesmon partially inhibits PAK phosphorylation. Phosphorylated caldesmon displays a modest reduction in affinity for actintropomyosin but is significantly less effective in inhibiting actin-activated S1 ATPase activity in the presence of tropomyosin. We conclude that PAK-phosphorylation of caldesmon at the calmodulin-binding sites modulates caldesmon inhibition of actin-myosin ATPase activity and may, in concert with the actions of Rho-kinase, contribute to the regulation of Ca2+ sensitivity of smooth muscle contraction.
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U2 - 10.1074/jbc.275.3.1959
DO - 10.1074/jbc.275.3.1959
M3 - Article
C2 - 10636898
AN - SCOPUS:0034695554
SN - 0021-9258
VL - 275
SP - 1959
EP - 1965
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 3
ER -