Orai1 and Orai2 mediate store-operated calcium entry that regulates HL60 cell migration and FAK phosphorylation

Store-operated Ca²⁺ entry (SOCE) is a major mechanism for the regulation of intracellular Ca²⁺ homeostasis and cellular function. Emerging evidence has revealed that altered expression and function of the molecular determinants of SOCE play a critical role in the development or maintenance of several cancer hallmarks, including enhanced proliferation and migration. Here we show that, in the acute myeloid leukemia cell line HL60, Orai2 is highly expressed at the transcript level, followed by the expression of Orai1. Using fluorescence Ca²⁺ imaging we found that Orai2 silencing significantly attenuated thapsigargin-induced SOCE, as well as knockdown of Orai1, while silencing the expression of both channels almost completely reduced SOCE, thus suggesting that SOCE in these cells is strongly dependent on Orai1 and Orai2. On the other hand, the expression of TRPC1, TRPC3 and TRPC6 is almost absent at the transcript and protein level. Bromodeoxyuridine cell proliferation assay revealed that Orai1 and Orai2 expression silencing significantly reduced HL60 cell proliferation. Furthermore, knockdown of Orai1 and Orai2 significantly attenuated the ability of HL60 to migrate in vitro as determined by transwell migration assay, probably due to the impairment of FAK tyrosine phosphorylation. These findings provide evidence for a role for Orai1 and Orai2, in SOCE and migration in the human HL60 promyeloblastic cell line. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.