CALHM1 controls the Ca2+-dependent MEK, ERK, RSK and MSK signaling cascade in neurons

Abstract

Calcium homeostasis modulator 1 (CALHM1) is a Ca2+ channel controlling neuronal excitability and potentially involved in the pathogenesis of Alzheimer's disease (AD). Although strong evidence indicates that CALHM1 is required for neuronal electrical activity, its role in intracellular Ca2+ signaling remains unknown. Here, we show that in hippocampal HT-22 cells, CALHM1 expression led to a robust and relatively selective activation of the Ca2+-sensing kinases, ERK1/2. CALHM1 also triggered activation of MEK1/2, the upstream ERK1/2-activating kinases, and of RSK1/2/3 and MSK1, two downstream effectors of ERK1/2 signaling. CALHM1-mediated activation of ERK1/2 signaling was controlled by the small GTPase Ras. Pharmacological inhibition of CALHM1 permeability using ruthenium red, Zn2+, and Gd3+, or expression of the CALHM1 N140A and W114A mutants, which are deficient in mediating Ca2+ influx, prevented the effect of CALHM1 on the MEK/ERK/RSK/MSK signaling cascade, demonstrating that CALHM1 controlled this pathway via its Ca2+ channel properties. Importantly, expression of CALHM1 bearing the natural P86L polymorphism, which leads to a partial loss of CALHM1 function and is associated with an earlier age at onset in AD patients, showed reduced activation of ERK1/2, RSK1/2/3, and MSK1. In line with these results obtained in transfected cells, primary cerebral neurons isolated from Calhm1 knockout mice showed significant impairments in the activation of MEK/ERK/RSK/MSK signaling. This work identifies a previously uncharacterized mechanism of control of Ca2+-dependent ERK1/2 signaling in neurons, and further establishes CALHM1 as a critical ion channel for neuronal signaling and function.

CALHM1 ion channel elicits amyloid-β clearance by insulin-degrading enzyme in cell lines and in vivo in the mouse brain

“…, at concentrations inhibiting CALHM1 permeability (Dreses-Werringloer et al, 2013;Ma et al, 2012), blocked the effect of CALHM1 on Aβ accumulation (Fig. 1D,E).…”

“…However, the non-specific inorganic dye Ruthenium Red or the ion Zn 2+ can fully inhibit CALHM1 currents and CALHM1-mediated [Ca 2+ ] i increase (Dreses-Werringloer et al, 2013;Ma et al, 2012). Ruthenium Red and Zn…”

“…Two conserved residues in the third hydrophobic domain of CALHM1, Trp114 (Dreses-Werringloer et al, 2013) and Asp121 (Ma et al, 2012), have also been identified as being potentially important for pore formation and/or ion permeation of the channel. Indeed, mutation of Trp114 to an alanine residue (W114A) and Asp121 to an arginine residue (D121R) have been found to fully block CALHM1-mediated Ca 2+ influx (Dreses-Werringloer et al, 2013) and CALHM1 currents (Ma et al, 2012), respectively. Fig.…”

“…Calhm1-KO mice were recently generated in our laboratory and are viable and fertile (Dreses-Werringloer et al, 2013;Ma et al, 2012;Taruno et al, 2013). Histological analyses have revealed that Calhm1 KO mice display no defects in brain development or brain integrity in adulthood (P.M. and V.V.…”

CALHM1 and its polymorphism P86L differentially control Ca2+ homeostasis, mitogen‐activated protein kinase signaling, and cell vulnerability upon exposure to amyloid β

“…Changes in phosphorylation of ERK in CALHM1 and P86L‐CALHM1 were also recently described by Dreses‐Werringloer et al . (2013). …”