Leu27IGF2 plays an opposite role to IGF1 to induce H9c2 cardiomyoblast cell apoptosis via Gαq signaling

Abstract

This study examines the role of IGF2/mannose 6-phosphate receptor (IGF2R) signaling in the signaling transduction regulation and cell apoptosis in H9c2 cardiomyoblast cells. However, it is difficult to recognize the distinct activation of IGF2 signaling without interfacing with IGFI receptor (IGF1R) after exposure to IGF2. Leu27IGF2, an analog of IGF2 that interacts selectively with the IGF2R, was used to specifically activate IGF2R signaling in this study. DNA fragmentation and TUNEL assay revealed that in contrast to IGF1 treatment preventing angiotensin II and AG1024-induced cell apoptosis, Leu27IGF2 appears to synergistically increase apoptosis in those cells. We further found cell apoptosis induction and an increase in the active form of caspase 3 in the treatment of cells with Leu27IGF2, but not IGF1. To detect the interaction between IGF2R and Gaq using the immunoprecipitation assay, we found that IGF2R could directly interact with Gaq and after treatment with Leu27IGF2 the binding ability of Gaq to IGF2R had increased. This sequentially resulted in the phosphorylation of phospholipase C-b, a key downstream modulator of Gaq, on serine 537. Moreover, disruption of the Gaq protein by small interferon RNA reduced the cell apoptosis induced by Leu27IGF2. Our findings demonstrate that IGF2R activation appears to induce cell apoptosis via Gaq-deriving signaling cascades and its effect is completely different from IGF1R survival signaling.

Histone acetylation is essential for ANG‐II‐induced IGF‐IIR gene expression in H9c2 cardiomyoblast cells and pathologically hypertensive rat heart

“…2c,d). Consistent with our previous studies (Chang et al, 2008;Chu et al, 2008;Chen et al, 2009;Chu et al, 2009a,b), all of these results suggest that IGF-IIR up-regulation might be the critical factor that promotes heart disease progression.…”

“…In the heart, the IGF-IIR disruption leads to cellular protection against cardiomyocyte apoptosis (Chen et al, 2004) and IGF-II and IGF-IIR up regulation in cardiomyocytes have been identified in a variety of heart disease models (Lee et al, 2006;Chang et al, 2008;Chu et al, 2008Chu et al, , 2009b. IGF-IIR could also function as a G proteincoupled receptor to trigger its downstream signaling modulators such as PKC-a/CaMKII, calcineurin and MMP/ TIMP, contributing to heart failure progression (Chang et al, 2008;Chu et al, 2008Chu et al, , 2009aChen et al, 2009). The upregulation of IGF-IIR gene expression occurred in this study after treatment with ANGII, LPS, inomycin, and TNF-a (Fig.…”

“…Results from specifically activated IGF-IIR signaling through either inhibition of the IGF-I receptor (IGF-IR) activity by IGF-IR siRNA and AG1024 (a chemical kinase inhibitor for IGF-IR) or using Leu27IGF-II analog, reveal that IGF-IIR activated by IGF-II binding acted like a G protein-coupled receptor to activate PKC-a/CaMKII and calcineurin by association with Gaq, leading to pathological hypertrophy and mitochondriadependent cell apoptosis in cardiomyocytes (Chen et al, 2009;Chu et al, 2009a,b). Additionally, IGF-IIR signaling activation causes the unbalance of matrix metallopeptidase 9 (MMP-9)/ tissue inhibitor of metalloproteinase 2 (TIMP-2) expression and increased plasminogen activator (PAs) expression (Chang et al, 2008), resulting in the development of myocardial remodeling.…”

ANG II promotes IGF-IIR expression and cardiomyocyte apoptosis by inhibiting HSF1 via JNK activation and SIRT1 degradation

“…Similarly, recent studies have reported that HSF1 acts as a transcriptional repressor of certain cytokine genes, including TNF-a and IL-1b, to prevent LPS-induced inflammation. 29,43,44 These results support our findings that HSF1 protects cardiomyocytes via transcriptional repression of IGF-IIR expression. Our results demonstrate that ANG II represses HSF1 by two mechanisms: (1) phosphorylation of HSF1 Ser303 to inhibit its transcriptional activity and (2) acetylation of HSF1 Lys80 to suppress its DNA-binding activity.…”

“…These findings support our previous studies. 10,14,29 We also observed that other kinases downstream of AT 1 R were involved in IGF-IIR expression. However, these kinases may have influenced IGF-IIR expression via different mechanisms, such as protein stability and degradation.…”