Role of the integrin-linked kinase/PINCH1/alpha-parvin complex in cardiac myocyte hypertrophy

Abstract

Outside-in signaling from fibronectin (FN) through integrin receptors has been shown to play an important role in promoting cardiac myocyte hypertrophy and synergizes with other hypertrophic stimuli such as the alphaadrenergic agonist phenylephrine (PE) and mechanical strain. The integrin-linked kinase (ILK) is a critical molecule involved in cell adhesion, motility and survival in nonmyocytes such as fibroblasts and epithelial cells. Its role in cardiac myocytes is unclear. In this study, we demonstrate that (1) ILK forms a complex with PINCH1 and alpha-parvin proteins (IPAP1 complex) in neonatal rat ventricular myocytes; (2) localization of IPAP1 complex proteins to costameres in cardiac myocytes is stimulated by FN, PE and synergistically by the combination of FN and PE in an integrin b1-dependent manner; (3) a dominant-negative mutant lacking the PINCH-binding N-terminus of ILK (ILK-C) prevents costamere association of ILK and alpha-parvin, but not PINCH1; (4) FN-and PE-induced hypertrophy, measured by increased protein/DNA ratio, beating frequency and atrial natriuretic peptide expression, is stimulated by low levels of ILK-C but repressed by high ILK-C expression; and (5) overexpression of ILK-C, as well as deletion of the ILK gene in mouse neonatal ventricular myocytes, induces marked apoptosis of cardiac myocytes. These results suggest that the IPAP1 complex plays an important role in mediating integrin-signaling pathways that regulate cardiac myocyte hypertrophy and resistance to apoptosis.

Silencing of Sodium–Hydrogen Exchanger 1 Attenuates the Proliferation, Hypertrophy, and Migration of Pulmonary Artery Smooth Muscle Cells via E2F1

“…We found that silencing the NHE1 gene significantly decreased the hypoxia-increased size of human PASMCs. In addition to cell size, cell volume, established by calculating the protein/DNA ratio, was used for the analysis of cell hypertrophy (39), because research indicates that the stimulation of protein synthesis without DNA replication is a feature of hypertrophy (33). We found that silencing NHE1 significantly decreased the protein/DNA ratio in human PASMCs cultured under hypoxia.…”

“…For the analysis of protein/DNA ratios, PASMCs were plated in six-well plates. After the transfection of NHE1 siRNA and exposure to hypoxia, PASMCs were harvested, and the protein/DNA ratio was determined by measuring total DNA content and total protein content (33,34).…”

Loss of Cardiomyocyte Integrin-Linked Kinase Produces an Arrhythmogenic Cardiomyopathy in Mice

“…16 ILK is upstream to a wide range of protein kinases involved in cell growth and cardiac hypertrophy, including protein kinase B, glycogen synthase kinase-3-β, extracellular signal-related kinase, and mammalian target of rapamycin 2 and ILK deletion causes severe cardiomyocyte apoptosis. 17 ILK is upregulated in human cardiac hypertrophy caused by left ventricular outflow obstruction, along with a wide range of hypertrophic genes. 4 ILK gene transfer improves cardiac function in post-MI and doxorubicin-induced cardiomyopathies.…”

PINCH Proteins Regulate Cardiac Contractility by Modulating Integrin-Linked Kinase-Protein Kinase B Signaling

“…Many of the currently known ILK-mediated functions require additional cofactors and interacting proteins. Increasing focus has therefore been put on the roles of the ternary complex comprising the proteins ILK, ␣-, ␤-, or ␥-parvin, and PINCH, PINCH1 or PINCH2 (5,26,30,34).…”

“…Many of the currently known ILK-mediated functions require additional cofactors and interacting proteins. Increasing focus has therefore been put on the roles of the ternary complex comprising the proteins ILK, ␣-, ␤-, or ␥-parvin, and PINCH, PINCH1 or PINCH2 (5,26,30,34).The ILK-parvin-PINCH (IPP) complex provides physical linkage between integrin transmembrane receptors and the actin cytoskeleton and serves as a signaling mediator that transduces mechanical signals to downstream effectors (32). PINCH and parvins do not have catalytic activity but rather function as adapters for other signaling molecules such as Nck-2 and Ras suppressor 1 (RSU-1), through which PINCH can regulate c-Jun N-terminal kinase (JNK) (7,25).…”