Phosphorylation of MYPT1 by protein kinase C attenuates interaction with PP1 catalytic subunit and the 20 kDa light chain of myosin

[摘要]

The effect of phosphorylation in the N-terminal region of myosin phosphatase target subunit 1 (MYPT1) on the interactions with protein phosphatase 1 catalytic subunit (PP1c) and with phosphorylated 20 kDa myosin light chain (P-MLC20) was studied. Protein kinase C (PKC) phosphorylated threonine-34 (1 mol/mol), the residue preceding the consensus PP1c-binding motif (³⁵KVKF³⁸) in MYPT1^1–38, but this did not affect binding of the peptide to PP1c. PKC incorporated 2 mol P_i into MYPT1^1–296 suggesting a second site of phosphorylation within the ankyrin repeats (residues 40–296). This phosphorylation diminished the stimulatory effect of MYPT1^1–296 on the P-MLC20 phosphatase activity of PP1c. Binding of PP1c or P-MLC20 to phosphorylated MYPT1^1–296 was also attenuated. It is concluded that phosphorylation of MYPT1 by PKC may therefore result in altered dephosphorylation of myosin.

[学科分类] 生物化学/生物物理

[关键词] Myosin phosphatase;Protein phosphatase 1;Myosin phosphatase target subunit 1;Protein kinase C;Ankyrin repeat;MC-LR;microcystin-LR;MLC20;20 kDa light chain of smooth muscle myosin;MLCK;myosin light chain kinase;MP;myosin phosphatase;MYPT1;myosin phosphatase target subunit 1;PBS;phosphate-buffered saline;PKA;cAMP-dependent protein kinase;P-MLC20;phosphorylated form of MLC20;PP1;type 1 protein phosphatase;PP1c;catalytic subunit of type 1 protein phosphatase;rPP1c;recombinant PP1c (δ isoform) expressed as a hexahistidine-tagged protein in Escherichia coli;SPR;surface plasmon resonance;PKC;protein kinase C