Disease relevance of PPP1R14A

• Analysis of the expression and phosphorylation of Ca(2+)-sensitizing proteins (MYPT1 and CPI-17) in vessels from rats and patients with cirrhosis suggested decreased Ca2+ sensitivity [1].
• PPP1R14A gene copy number variants (CNV) and gene expression are both decreased in colorectal carcinoma samples  [2] [3]

High impact information on PPP1R14A

• Phosphorylation of CPI-17 in rabbit arteries was enhanced by calyculin A but not okadaic acid or fostriecin, consistent with PP1-mediated dephosphorylation [4].
• Phosphoprotein inhibitor CPI-17 specificity depends on allosteric regulation of protein phosphatase-1 by regulatory subunits [4].
• We propose that CPI-17 binds at the PP1 active site where it is dephosphorylated, but association of MYPT1 with PP1C allosterically retards this hydrolysis, resulting in formation of a complex of MYPT1.PP1C.P-CPI-17, leading to an increase in smooth muscle contraction [4].
• Exposure to histamine (100 microM; 10 minutes) led to phosphorylation of MLC (134% relative to untreated cells) and of CPI-17 [5].
• RT-PCR and Western blot analyses were performed to determine RhoA, ROCK-II, CPI-17, MYPT1, and myosin light-chain 20 (MLC(20)) [6].

Biological context of PPP1R14A

• Identification of human, mouse and rat PPP1R14A, protein phosphatase-1 inhibitor subunit 14A, & mapping human PPP1R14A to chromosome 19q13.13-q13.2 [7].
• Histamine caused stronger CPI-17 phosphorylation than thrombin [8].
• To elucidate the role of CPI-17 in the regulation of endothelial cytoskeleton, full-length CPI-17 plasmid was transiently transfected into pulmonary artery endothelial cells, where the background of endogenous protein is low [8].
• As well as the native CPI17 from porcine aorta, the recombinant protein completely suppressed the PP1 activity (IC50 = 0.18 nM) by the stoichiometric thiophosphorylation [9].
• The coding region represented the complete amino acid sequence of this protein comprised of a novel 147-residue polypeptide, which we termed CPI17, a 17-kDa PKC-potentiated inhibitory protein of PP1 [9].

Anatomical context of PPP1R14A

• The distribution of mouse and rat PPP1R14A was more specific and different from that of human PPP1R14A, abundant in lung, moderate/abundant in testis, moderate in brain and low in heart [7].
• Northern blot analysis showed that human PPP1R14A was highly expressed as a 600 bp transcript in heart, prostate, testis, ovary, colon, small intestine and pancreas, lowly in brain, placenta, skeletal muscle and spleen and lung [7].
• In this study we found that, similar to smooth muscle, lung microvascular endothelial cells expressed specific endogenous inhibitor of MLCP, CPI-17 [8].
• CPI-17 had no effect on cytoskeleton under nonstimulating conditions [8].
• The CPI17 mRNA is expressed in smooth muscle tissues such as aorta and bladder, whereas little expression was observed in heart, skeletal muscle, and non-muscle tissues [9].

Associations of PPP1R14A with chemical compounds

• Together these data suggest the potential importance of PKC/CPI-17-mediated pathway in histamine-triggered cytoskeletal rearrangements leading to lung microvascular barrier compromise [8].
• CPI-17 interacted with the cysteine-rich domain of PKC and was phosphorylated by all PKC isotypes [10].
• Phosphorylated CPI-17 at threonine-38 residue (p(Thr38)-CPI-17), MYPT1 at threonine-696 residue (p(Thr696)-MYPT1), and MLC(20) at threonine-18/serine-19 residues (p(Thr18/Ser19)-MLC(20)) were also determined in the basal state and after pretreatment with the ROK inhibitor Y 27632 [6].
• Thus, CPI-17 as a substrate of Rho-kinase could be involved in the Ca(2+) sensitization of smooth muscle contraction as a downstream effector of Rho-kinase [11].
• Forskolin, dbcAMP, and isoproterenol inhibited KCl-induced Rho activation and phosphorylation of MYPT1 and CPI-17 [12].

Regulatory relationships of PPP1R14A

• ILK activity, and CPI-17 and MLC20 phosphorylation were inhibited by LY294002 and in muscle cells expressing ILK(R211A) or treated with siRNA (small interfering RNA) for ILK [13].
• Augmentation of endothelin-1-induced phosphorylation of CPI-17 and myosin light chain in bronchial smooth muscle from airway hyperresponsive rats [14].

Other interactions of PPP1R14A

• Inhibitory analysis revealed that PKC more significantly contributes to agonist-induced CPI-17 phosphorylation than Rho-kinase [8].
• Association of CPI-17 with protein kinase C and casein kinase I [10].
• ACh acting via M2 receptors activated ILK, and induced CPI-17 and MLC20 phosphorylation and muscle contraction, but only after inhibition of p38 MAPK; all these responses were inhibited in cells expressing ILK(R211A) [13].
• Sustained contraction via G(i)-coupled receptors is dependent on CPI-17 and MLC20 phosphorylation by ILK [13].
• Phosphorylation of CPI-17 and PHI-1 by the MYPT1-associated kinase (M110 kinase) was investigated [15].

Analytical, diagnostic and therapeutic context of PPP1R14A

• In addition, we mapped human PPP1R14A to chromosome 19q13.13-q13.2 by radiation hybrid mapping, and determined that the human PPP1R14A gene spanned a 5.1-kb region and consisted of four exons and three introns [7].
• Molecular cloning of a novel phosphorylation-dependent inhibitory protein of protein phosphatase-1 (CPI17) in smooth muscle: its specific localization in smooth muscle [9].

References