Potential mechanisms of calcium dependent regulation of the mammalian cell cycle revealed by comprehensive unbiased label-free nLC-MS/MS quantitative proteomics.

Calcium (Ca2+ ) controls progression through the mammalian cell cycle by engaging a diverse range of molecular pathways. While the essential role of spatio-temporal Ca2+ signalling in the cell cycle is well established, the precise mechanisms by which it regulates cell cycle entry and progression through G1 are not particularly well understood. Here, high-resolution label-free semi-quantitative nLC-MS/MS analysis has been used to support a highly reproducible unbiased analysis of Ca2+ influx dependent growth factor induced protein expression early in G1 in human fibroblasts. Using this strategy a panel of 182 proteins whose expression was Ca2+ dependent were identified. Pathway analysis has indicated that Ca2+ likely regulates cell proliferation via PI3K/AKT pathway and its downstream target mTOR. In addition to cell proliferation found proteins were involved in the regulation of cell morphology and cellular assembly and organization, the environmental clues, which are known to regulate G1 progression. Reported here data represents one of the most comprehensive proteomic datasets of growth factor and Ca2+ dependent protein expression in the mammalian cell cycle and provides a rich source of publically available data to support continued investigation of the role of Ca2+ in G1 progression at both the molecular and systems level.

BIOLOGICAL SIGNIFICANCE: The results of this study provide new insight into Ca2+ dependent regulation of cell cycle. This manuscript reports first to date global analysis of Ca2+ regulated protein expression changes early in G1 in non-transformed human fibroblast cell line. It also highlights canonical signalling pathways and biological processes that are regulated by the inhibition of Ca2+ influx. Importantly, it appears that Ca2+ may be the factor that links cell division with environmental cues, cell morphology and cellular assembly and organization, on which cell proliferation depends. Hence, the findings presented here provide numerous opportunities for more detailed investigations of the mechanism of Ca2+ dependent regulation of cell cycle at the molecular and systemic level.