title: Cooperativity between inhibition of cytosolic K+ efflux and AMPK activation during suppression of hypoxia-induced cellular apoptosis.
abstract: Cellular potassium homeostasis has recently emerged as a critical regulator of apoptosis in response to variety of stimuli. However, functional hierarchy of this phenomenon in the apoptotic cascade and therefore, its significance as a pathway for intervention is not fully established. Chronic hypoxia, a known threat to cell survival, also modulates cellular potassium homeostasis. In this study, we tested if hypoxia-induced apoptosis in lymphocytes can be prevented by modulating cellular K+ homeostasis. We observed that chronic hypoxia accelerated the rate of apoptosis in resting murine splenocytes concomitant with cytosolic K+ efflux. We tested several modalities including elevated extracellular potassium besides various K+ channel inhibitors to curtail hypoxia-induced K+ efflux and interestingly, established that the supplementation of KCl in extracellular medium was most effective in preventing hypoxia-induced apoptosis in these cells. Subsequent mechanistic dissection of pathways underlying this phenomenon revealed that besides effectively inhibiting hypoxia-induced efflux of K+ ion and its downstream cell-physiological consequences; elevated extracellular KCl modulated steady state levels of cellular ATP and culminated in stabilization of AMPKα with pro-survival consequences. Also, interestingly, global gene expression profiling revealed that KCl supplementation down regulated a distinct p53-regulated cellular sub-network of genes involved in regulation of DNA replication. Additionally, we present experimental evidence for the functional role of AMPK and p53 activation during suppression of hypoxia-induced apoptosis. In conclusion, our study highlights a novel bimodal effect wherein cooperativity between restoration of K+ homeostasis and a sustainable 'metabolic quiescence' induced by AMPK activation appeared indispensible for curtailing hypoxia-induced apoptosis.
authors: Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences (DIPAS), DRDO, Delhi, India.
authors: Nomesh K
authors: NK
authors: Gopalani
authors: Ram Niwas
authors: RN
authors: Meena
authors: Dipti N
authors: DN
authors: Prasad
authors: Govindaswamy
authors: G
authors: Ilavazhagan
authors: Manish
authors: M
authors: Sharma
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D016196:S Phase / Q000187:drug effects / Q000502:physiology; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D016159:Tumor Suppressor Protein p53; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D055372:AMP-Activated Protein Kinases; D011188:Potassium