Nonmuscle myosin phosphorylation sites for calcium-dependent and calcium-independent protein kinases

Hassell, Tommy C.; Kemp, Bruce E.; Masaracchia, Ruthann A.

doi:10.1016/0006-291x(86)90553-x

Cited by 13 publications

(9 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, both PAK and MLCK phosphorylation of the RLC in intact nonmuscle myosin II activates the myosin ATPase (10). These results in nonmuscle cells are supported by observations of Van Eyk et al (8) in smooth muscle cells, suggesting that PAK and MLCK phosphorylation of RLC both contribute to smooth muscle contraction.…”

supporting

confidence: 79%

“…The sequences at both phosphorylation sites are consistent with the specificity determinants identified in previous studies (27)(28)(29). Phosphorylation of synthetic peptides from the PAK substrates H4 (27), S6 (28), and RLC (10,29) has demonstrated that optimum reactivity is observed with Arg at position P-1 or P-3. In addition, the presence of a second basic residue at P-1 to P-3 enhances substrate phosphorylation (10,27).…”

Section: Pak2supporting

confidence: 68%

“…No activation or regulation by calcium has been described for these protein kinases. Initial evidence that one substrate of PAK is the nonmuscle myosin II was reported over a decade ago (10). Since PAK2 activation by Cdc42/rac-GTP was not known at that time, activation in the initial studies was accomplished by in situ production of the PAK catalytic core by limited trypsin digestion.…”

Section: Discussionmentioning

confidence: 99%

“…Phosphorylation of synthetic peptides from the PAK substrates H4 (27), S6 (28), and RLC (10,29) has demonstrated that optimum reactivity is observed with Arg at position P-1 or P-3. In addition, the presence of a second basic residue at P-1 to P-3 enhances substrate phosphorylation (10,27). Several, but not all, substrates also contain viscinal Ser/Thr residues at the phosphorylation sites (28,29).…”

Section: Pak2mentioning

confidence: 99%

“…Permeabilized endothelial cells incubated with Cdc42-activated PAK2 or the catalytic domain of PAK2 underwent ATP-dependent retraction and actin reorganization (6). In addition, these studies using purified enzymes established that the regulatory nonmuscle and smooth muscle myosin II light chain is a substrate for PAK2 (9,10). Recent studies have shown that the PAK family of kinases is involved in activation of myosin II in vivo.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Phosphorylation of Myosin Light Chain Kinase by p21-activated Kinase PAK2

Goeckeler¹,

Masaracchia²,

Zeng³

et al. 2000

Journal of Biological Chemistry

Self Cite

138

124

View full text Add to dashboard Cite

Phosphorylation of myosin II regulatory light chains (RLC) by Ca2؉ /calmodulin-dependent myosin light chain kinase (MLCK) is a critical step in the initiation of smooth muscle and non-muscle cell contraction. Posttranslational modifications to MLCK down-regulate enzyme activity, suppressing RLC phosphorylation, myosin II activation, and tension development. Here we report that PAK2, a member of the Rho family of GTPasedependent kinases, regulates isometric tension development and myosin II RLC phosphorylation in saponin permeabilized endothelial monolayers. PAK2 blunts tension development by 75% while inhibiting diphosphorylation of myosin II RLC. Cdc42-activated placenta and recombinant, constitutively active PAK2 phosphorylate MLCK in vitro with a stoichiometry of 1.71 ؎ 0.21 mol of PO 4 /mol of MLCK. This phosphorylation inhibits MLCK phosphorylation of myosin II RLC. PAK2 catalyzes MLCK phosphorylation on serine residues 439 and 991. Binding calmodulin to MLCK blocks phosphorylation of Ser-991 by PAK2. These results demonstrate that PAK2 can directly phosphorylate MLCK, inhibiting its activity and limiting the development of isometric tension.The PAK 1 family of serine/threonine protein kinases have been implicated in a broad spectrum of signal transduction pathways leading to diverse physiological end points, including cytoskeletal reorganization, apoptosis, and Ras-mediated cell transformation (1, 2). All PAK isoforms are direct effectors of the Rho family GTP-binding proteins Rac and Cdc42, suggesting that cell-specific responses arise from either selective regulation of G protein activation in response to unique agonists or selective phosphorylation of tissue-specific protein kinase substrates.In the initial studies of the relative roles of G protein activation and protein kinase activity in actin reorganization, Sells et al. (3) demonstrated that microinjection of activated PAK1 induced rapid formation of polarized filopodia in Swiss 3T3 cells. However, the relative importance of PAK-dependent phosphorylation of unique substrates during Cdc42/Racdependent cytoskeletal reorganization is incompletely understood. Transient transfection of HeLa cells with constitutively active PAK1 promoted cytoskeletal rearrangement, which was entirely analogous to that observed in Cdc42 and Rac transfected cells (4). In subsequent studies, a peptide that inhibited kinase activity in PAK blocked Cdc42, Rac, and constitutively active PAK-induced morphological changes in transfected HeLa cells (5). An important role for PAK-mediated phosphorylation in actin reorganization has also been supported by studies in permeabilized (6) and intact (7) endothelial cells as well as skinned smooth muscle cells (8). Permeabilized endothelial cells incubated with Cdc42-activated PAK2 or the catalytic domain of PAK2 underwent ATP-dependent retraction and actin reorganization (6). In addition, these studies using purified enzymes established that the regulatory nonmuscle and smooth muscle myosin II light chain is a substrate for PAK2 (9, 1...

show abstract

supporting

confidence: 79%