ERK1/2 activation in heart is controlled by melusin, focal adhesion kinase and the scaffold protein IQGAP1

Abstract

SummaryExtracellular signal-regulated kinase 1/2 (ERK1/2) signalling is a key pathway in cardiomyocyte hypertrophy and survival in response to many different stress stimuli. We have previously characterized melusin as a muscle-specific chaperone protein capable of ERK1/2 signalling activation in the heart. Here, we show that in the heart, melusin forms a supramolecular complex with the proto-oncogene c-Raf, MEK1/2 (also known as MAPKK1/2) and ERK1/2 and that melusin-bound mitogen-activated protein kinases (MAPKs) are activated by pressure overload. Moreover, we demonstrate that both focal adhesion kinase (FAK) and IQ motif-containing GTPase activating protein 1 (IQGAP1), a scaffold protein for the ERK1/2 signalling cascade, are part of the melusin complex and are required for ERK1/2 activation in response to pressure overload. Finally, analysis of isolated neonatal cardiomyocytes indicates that both FAK and IQGAP1 regulate melusin-dependent cardiomyocyte hypertrophy and survival through ERK1/2 activation.

Overexpression of the muscle-specific protein, melusin, protects from cardiac ischemia/reperfusion injury

“…In addition, Melusin also organizes a signalosome complex regulating the ERK1/2 pathway [20]. We have shown, in fact, that melusin interacts with c-Raf, MEK1/2 and ERK1/2 MAP Kinases, as well as with their scaffold molecule IQGAP-1 [55]. An additional key element also present in the complex is the focal adhesion kinase FAK.…”

“…At the same time, via BAD phosphorylation it protects cell from apoptosis, a major cause of tissue damage in reperfusion injury [1,17,21,39,71]. In addition ERK signaling is well known to promote cell survival in different cell types including cardiomyocytes [44,55,59]. The MEK/ERK cascade: from signaling specificity to diverse functions [64].…”

“…Male WT and transgenic littermate FVB mice (Mel-TG) [15] weighing between 25-35 g (10-15 weeks old) were given 500 U heparin and anesthetized with sodium pentothal (50 mg/kg) by intraperitoneal injections before being culled by cervical dislocation [55,56] 2 . The temperature of the perfusion system was maintained at 37°C.…”

“…For Western blotting, hearts were lysed in Tris-buffered saline with 1% Triton X-100, plus Roche complete protease inhibitor cocktail containing (mM) NaF 10, PMSF 1 and Na 3 VO 4 1. Protein extracts were clarified with three sequential centrifugations for 20 minutes at 20,000 g, at 4°C [55,56]. Western blot band quantifications were performed with Quantity One software (BioRad).…”

Morgana and melusin: Two fairies chaperoning signal transduction

“…3A). 37 Interestingly, in vivo analysis on transgenic mice subjected to surgical banding of the aorta demonstrated that melusinbound ERK1/2 is activated following biomechanical stress in a FAK-and MEK1/2-dependent manner (Fig. 3B).…”