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Protein phosphatase 1 regulatory subunit 14A also known as CPI-17 (C-kinase potentiated Protein phosphatase-1 Inhibitor Mr = 17 kDa) is a protein that in humans is encoded by the PPP1R14Agene.
Function
CPI-17 is a phosphorylation-dependent inhibitor protein of smooth muscle myosin phosphatase, discovered in pig aortic homogenates. Phosphorylation of the Thr-38 residue converts the protein into a potent inhibitor for myosin phosphatase. A single phosphorylation of CPI-17 at Thr-38 triggers a global conformational change that causes re-alignment of four helices. Multiple kinases are identified to phosphorylate CPI-17, such as PKC, ROCK, PKN, ZIPK, ILK, and PAK. Agonist stimulation of smooth muscle enhances CPI-17 phosphorylation mainly through PKC and ROCK. Myosin phosphatase inhibition increases myosin phosphorylation and smooth muscle contraction in the absence of increased intracellular Ca concentration. This phenomenon is known as Ca sensitization, which occurs in response to agonist stimulation of smooth muscle. In Purkinje neuron, CPI-17 is involved in long-term synaptic depression.
CPI-17 is up-regulated some cancer cells, and causes hyperphosphorylation of tumor suppressor merlin/NF2. In prostate cancer, CPI-17 expressions are reported to be associated with GWAS risk SNP rs7247241 T allele and increase cell proliferation.
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