ROLE OF STORE-OPERATED CALCIUM ENTRY DURING MEIOTIC PROGRESSION AND FERTILIZATION OF MAMMALIAN OOCYTES

Calcium signaling is essential for many cellular events, including muscle contraction, secretion of hormones and neurotransmitters, and fertilization of oocytes. For the appropriate maturation and fertilization of mammalian oocytes, the influx of extracellular calcium through plasma membrane Ca2+ channels is required. Although the molecular pathway of the Ca2+ entry in other cell types has been reported, Ca2+ channels involved in the regulation of Ca2+ influx in oocytes have remained unknown for a long time. In this review, we summarize recent findings regarding the occurrence of store-operated calcium entry (SOCE) in mammalian oocytes and the expression and localization profiles of STIM1 and ORAI1, two important proteins that control SOCE. As we discuss here, STIM1, as an endoplasmic reticulum Ca2+ sensor, and ORAI1 the major plasma Ca2+ channel involved in SOCE, might help to explain the role of Ca2+ entry in mammalian oocyte maturation and fertilization.