PH domain leucine-rich repeat protein phosphatase 2 (PHLPP2) regulates G-protein–coupled receptor kinase 5 (GRK5)-induced cardiac hypertrophy in vitro

Abstract

PH domain leucine-rich repeat protein phosphatase (PHLPP) is a serine/threonine phosphatase that has been shown to regulate cell growth and survival through dephosphorylation of several members of the AGC family of kinases. G-protein-coupled receptor kinase 5 (GRK5) is an AGC kinase that regulates phenylephrine (PE)-induced cardiac hypertrophy through its noncanonical function of directly targeting proteins to the nucleus to regulate transcription. Here we investigated the possibility that the PHLPP2 isoform can regulate GRK5-induced cardiomyocyte hypertrophy in neonatal rat ventricular myocytes (NRVMs). We show that removal of PHLPP2 by siRNA induces hypertrophic growth of NRVMs as measured by cell size changes at baseline, potentiated PE-induced cell size changes, and re-expression of fetal genes atrial natriuretic factor and brain natriuretic peptide. Endogenous GRK5 and PHLPP2 were found to interact in NRVMs, and PE-induced nuclear accumulation of GRK5 was enhanced upon down-regulation of PHLPP2. Conversely, overexpression of PHLPP2 blocked PE-induced hypertrophic growth, re-expression of fetal genes, and nuclear accumulation of GRK5, which depended on its phosphatase activity. Finally, using siRNA against GRK5, we found that GRK5 was necessary for the hypertrophic response induced by PHLPP2 knockdown. Our findings demonstrate for the first time a novel regulation of GRK5 by the phosphatase PHLPP2, which modulates hypertrophic growth. Understanding the signaling pathways affected by PHLPP2 has potential for new therapeutic targets in the treatment of cardiac hypertrophy and failure.

Targeting GRK5 for Treating Chronic Degenerative Diseases

“…Recently, GRK5 activity has been found regulated by PH domain leucine-rich repeat protein phosphatase (PHLPP), a Ser/Thr phosphatase involved in the dephosphorylation of several kinases. Interestingly, PHLPP was able to interact with GRK5 to modulate phenylephrine-induced nuclear accumulation of GRK5 and cardiac hypertrophy in neonatal rat ventricular myocytes (NRVMs) [ 59 ].…”

PHLPP2 as a novel metastatic and prognostic biomarker in non‐small cell lung cancer patients

“…PHLPP2, a pleckstrin homology domain leucine‐rich repeat protein phosphatases (PHLPP) isozyme, catalyzes the dephosphorylation of AGC kinases including Akt . Maintaining balanced levels of PHLPP2 expression is essential in preventing pathologies, as changes in steady‐state levels of PHLPP2 are correlated with many diseases including diabetes, hepatic steatosis and cancer . Recently, many studies have shown that PHLPP2 expression is ubiquitously lost in multiple cancers and plays a key role in a wide range of biological processes such as cancer cell proliferation, metastasis, autophagy and apoptosis …”

“…4 Maintaining balanced levels of PHLPP2 expression is essential in preventing pathologies, as changes in steadystate levels of PHLPP2 are correlated with many diseases including diabetes, hepatic steatosis and cancer. 5,6 Recently, many studies have shown that PHLPP2 expression is ubiquitously lost in multiple cancers and plays a key role in a wide range of biological processes such as cancer cell proliferation, metastasis, autophagy and apoptosis. [6][7][8][9][10][11][12] PHLPP2 regulates several cellular pathways in cancer.…”

“…5,6 Recently, many studies have shown that PHLPP2 expression is ubiquitously lost in multiple cancers and plays a key role in a wide range of biological processes such as cancer cell proliferation, metastasis, autophagy and apoptosis. [6][7][8][9][10][11][12] PHLPP2 regulates several cellular pathways in cancer. 13 Notably, direct dephosphorylation by PHLPP2 inactivates pro-oncogenic AGC kinases such as Akt, S6K, and PKC and activates pro-apoptotic kinases such as Mst1.…”

<p><em>miR-141</em> Promotes Colon Cancer Cell Proliferation by Targeted <em>PHLPP2</em> Expression Inhibitionn</p>

“…It is indispensable to keep PHLPP2 expression in balance for pathological prevention as the change of PHLPP2 steady-state level is connected with various diseases, including diabetes, hepatic steatosis and cancers. 16,17 Recently, many studies have unveiled that PHLPP2 is ubiquitously lost in various cancers and plays an important role in multiple biological processes, such as cancer cell proliferation, metastasis, autophagy and apoptosis. [18][19][20][21][22][23] Nonetheless, the diagnostic and prognostic significance of PHLPP2 in CC have not been fully researched.…”