Constitutive recycling of the store-operated Ca2+ channel Orai1 and its internalization during meiosis.
The egg's competency to activate at fertilization and transition to embryogenesis is dependent on its ability to generate a fertilization-specific Ca(2+) transient. To endow the egg with this capacity, Ca(2+) signals remodel during oocyte maturation, including inactivation of the primary Ca(2+) influx pathway store-operated Ca(2+) entry (SOCE). SOCE inactivation is coupled to internalization of the SOCE channel, Orai1. In this study, we show that Orai1 internalizes during meiosis through a caveolin (Cav)- and dynamin-dependent endocytic pathway. Cav binds to Orai1, and we map a Cav consensus-binding site in the Orai1 N terminus, which is required for Orai1 internalization. Furthermore, at rest, Orai1 actively recycles between an endosomal compartment and the cell membrane through a Rho-dependent endocytic pathway. A significant percentage of total Orai1 is intracellular at steady state. Store depletion completely shifts endosomal Orai1 to the cell membrane. These results define vesicular trafficking mechanisms in the oocyte that control Orai1 subcellular localization at steady state, during meiosis, and after store depletion.
Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City, Qatar Foundation, Doha, Qatar.
Fang
F
Yu
Lu
L
Sun
Khaled
K
Machaca
D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008540:Meiosis; D000071740:ORAI1 Protein; D009865:Oocytes / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
D015220:Calcium Channels; D000071740:ORAI1 Protein; C553970:ORAI1 protein, Xenopus; D029867:Xenopus Proteins; D049452:Green Fluorescent Proteins