SHP2-mediated signaling cascade through gp130 is essential for LIF-dependent ICaL, [Ca 2+] i transient, and APD increase in cardiomyocytes

Abstract

Leukemia inhibitory factor (LIF), a cardiac hypertrophic cytokine, increases L-type Ca 2+ current ( I CaL) via ERK-dependent and PKA-independent phosphorylation of serine 1829 in the Cav 1.2 subunit. The signaling cascade through gp130 is involved in this augmentation. However, there are two major cascades downstream of gp130, i.e. JAK/STAT3 and SHP2/ERK. In this study, we attempted to clarify which of these two cascades plays a more important role. Knock-in mouse line, in which the SHP2 signal was disrupted (gp130 F759/F759 group), and wild-type mice (WT group) were used. A whole-cell patch clamp experiment was performed, and intracellular Ca 2+ concentration ([Ca 2+] i transient) was monitored. The I CaL density and [Ca 2+] i transient were measured from the untreated cells and the cells treated with LIF or IL-6 and soluble IL-6 receptor (IL-6 + sIL-6r). Action potential duration (APD) was also recorded from the ventricle of each mouse, with or without LIF. Both LIF and IL-6 + sIL-6r increased I CaL density significantly in WT (+ 27.0%, n = 16 p < 0.05, and + 32.2%, n = 15, p < 0.05, respectively), but not in gp130 F759/F759 (+ 9.4%, n = 16, NS, and − 6.1%, n = 13, NS, respectively). Administration of LIF and IL-6 + sIL-6r increased [Ca 2+] i transient significantly in WT (+ 18.8%, n = 13, p < 0.05, and + 32.0%, n = 21, p < 0.05, respectively), but not in gp130 F759/F759 (− 3.8%, n = 7, NS, and − 6.4%, n = 10, NS, respectively). LIF prolonged APD 80 significantly in WT (10.5 ± 4.3%, n = 12, p < 0.05), but not in gp130 F759/F759 (− 2.1 ± 11.2%, n = 7, NS). SHP2-mediated signaling cascade is essential for the LIF and IL-6 + sIL-6r-dependent increase in I CaL, [Ca 2+] i transient and APD.