TRPC1-mediated Ca²⁺ entry is essential for the regulation of hypoxia and nutrient depletion-dependent autophagy.

P Sukumaran,Y Sun,M Vyas,B B Singh

doi:10.1038/cddis.2015.7

Abstract

Autophagy is a cellular catabolic process needed for the degradation and recycling of protein aggregates and damaged organelles. Although Ca2+ is suggested to have an important role in cell survival, the ion channel(s) involved in autophagy have not been identified. Here we demonstrate that increase in intracellular Ca2+ via transient receptor potential canonical channel-1 (TRPC1) regulates autophagy, thereby preventing cell death in two morphologically distinct cells lines. The addition of DMOG or DFO, a cell permeable hypoxia-mimetic agents, or serum starvation, induces autophagy in both epithelial and neuronal cells. The induction of autophagy increases Ca2+ entry via the TRPC1 channel, which was inhibited by the addition of 2APB and SKF96365. Importantly, TRPC1-mediated Ca2+ entry resulted in increased expression of autophagic markers that prevented cell death. Furthermore, hypoxia-mediated autophagy also increased TRPC1, but not STIM1 or Orai1, expression. Silencing of TRPC1 or inhibition of autophagy by 3-methyladenine, but not TRPC3, attenuated hypoxia-induced increase in intracellular Ca2+ influx, decreased autophagy, and increased cell death. Furthermore, the primary salivary gland cells isolated from mice exposed to hypoxic conditions also showed increased expression of TRPC1 as well as increase in Ca2+ entry along with increased expression of autophagic markers. Altogether, we provide evidence for the involvement of Ca2+ influx via TRPC1 in regulating autophagy to protect against cell death.

Highlights

Regulates autophagy, thereby preventing cell death in two morphologically distinct cells lines
Similar to our cell culture results, LC3A expression was increased in mice exhibiting hypoxia conditions (Figure 1e, quantification provided as bar graph) suggesting that hypoxia induces autophagy in mouse models
Autophagy is a major pathway needed for the clearance of pathogens in immunity and helps in maintaining cellular homeostasis.[15]

Summary

Introduction

Regulates autophagy, thereby preventing cell death in two morphologically distinct cells lines. TRPC1-mediated Ca2+ entry resulted in increased expression of autophagic markers that prevented cell death. Permeable channels, including families of TRPCs, Orais, voltage-gated, two-pore, mitochondrial Ca2+ uniporter, IP3, and ryanodine receptors have all been identified to contribute towards changes in intracellular Ca2+ ([Ca2+]i).[10,12,13,14] Channels of the TRPCs and Orai families have been related to several Ca2+-dependent physiological processes in various cell types, ranging from cell proliferation to contractility, to apoptosis under both physiological and pathological conditions.[12] it has been suggested that intracellular Ca2+ is one of the key regulators of autophagy;[15] the possible role of Ca2+ in autophagy is still inconclusive.

Methods

Results

Conclusion