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Extracellular acidification accompanies neoplastic transformation of tissues and increases with tumor aggressiveness [1, 2]. The intracellular signaling cascade triggered by this process remains poorly understood and may be linked to recently discovered proton-activated G protein-coupled receptors such as OGR1 and G2A [3, 4]. Here, we report that OGR1 and G2A are expressed in human medulloblastoma tissue and its corresponding neuronal cell line. We show that extracellular acidification activates phospholipase C, IP(3) formation, and subsequent Ca2+ release from thapsigargin-sensitive stores in neurons. The number of responsive cells and the amount of Ca2+ released from stores correlated positively with the extent of extracellular acidification. Ca2+ release recruited the MEK/ERK pathway, providing a mechanistic explanation for how acidification stimulates cell growth. In addition, acidification activated Ca2+-permeable ion channels through a mechanism dependent on phospholipase C but independent of store depletion or a cytoplasmic Ca2+ rise. Hence, extracellular acidification, to levels seen in tumor tissue, activates temporally and spatially distinct pathways that elevate Ca2+ and may be directly relevant for tumor cell biology.

Original publication

DOI

10.1016/j.cub.2008.04.049

Type

Journal article

Journal

Curr Biol

Publication Date

20/05/2008

Volume

18

Pages

781 - 785

Keywords

Calcium Signaling, Cell Cycle Proteins, Cell Line, Tumor, Cell Transformation, Neoplastic, Cerebellar Neoplasms, Extracellular Fluid, Humans, Hydrogen-Ion Concentration, Inositol 1,4,5-Trisphosphate, Medulloblastoma, Receptors, G-Protein-Coupled, Type C Phospholipases