The large conductance calcium‐activated potassium channel affects extrinsic and intrinsic mechanisms of apoptosis

Abstract

The large conductance calcium-activated K+ or BK channel underlies electrical signals in a number of different cell types. Studies show that BK activity can also serve to regulate cellular homeostasis by protecting cells from apoptosis due to events such as ischemia. Recent coimmunoprecipitation studies combined with mass spectrometry suggest putative protein partners that interact with BK to regulate intrinsic and extrinsic apoptotic pathways. Here, we test two of those partners to determine the effects on these two signaling pathways. Through reciprocal coimmunoprecipitation (coIP) experiments, we show that BK interacts with p53 and FADD both in mouse brain and when overexpressed in a heterologous expression system, such as HEK293 cells. Moreover, coIP experiments using N- and C-terminal fragments reveal that FADD interacts with the C-terminus of BK, whereas p53 interacts with either the N- or C-terminus. Immunolocalization studies show that BK colocalizes with p53 and FADD in the mitochondrion and plasmalemma, respectively. HEK293 cells that stably express BK are more resistant to apoptosis when p53 or FADD are overexpressed or when their intrinsic and extrinsic pathways are stimulated via Mitomycin C or TNF-related apoptosis-inducing ligand (TRAIL), respectively. Moreover, when stimulating with TRAIL, caspase 8 activation decreases in BK expressing cells. These data suggest that BK may be part of a larger complex of proteins that protect against apoptosis by interacting with pro-apoptotic proteins such as p53 and FADD.

BK Channels in the Central Nervous System

“…Pharmacological blockade or genetic inactivation of BK α also exacerbates NMDA-induced neurotoxicity in vivo and neuronal death in hippocampal or cerebrocortical slice cultures exposed to ischemia-like conditions, which further suggests that neuronal BK channels exert their neuroprotective effect by dampening excitotoxicity (Katsuki, Shinohara, Fujimoto, Kume, & Akaike, 2005; Liao et al, 2010; Runden-Pran et al, 2002). It is also possible that BK channels protect against neuronal death via their interactions with the proapoptotic proteins p53 and fas-associated protein with death domain (Sakai & Sokolowski, 2015). An additional mechanism may involve mitochondrial BK channels, which are known to play a critical cardioprotective role in ischemia–reperfusion injury of the heart (Singh et al, 2013; Xu et al, 2002; see Chapter “Functional Role of Mitochondrial and Nuclear BK Channels” by Gao and Li).…”

Defective Tmprss3-Associated Hair Cell Degeneration in Inner Ear Organoids

“…Mice lacking 14-3-3 ETA (a family member of 14-3-3-EPSILON) exhibit cochlear HC degeneration via apoptosis (Buret et al., 2016). Previous studies have demonstrated that inhibition of BK channels can cause cell apoptosis (Bortner and Cidlowski, 2014, Sakai and Sokolowski, 2015). Although no biological pathways were significantly enriched upon analysis of the DEGs, genes involved in both apoptosis and cell survival were revealed after further exploring potential interactions using IPA (Figures S5G and S5H.).…”