Internalization of plasma membrane Ca2+-ATPase during Xenopus oocyte maturation.
A transient increase in intracellular Ca(2+) is the universal signal for egg activation at fertilization. Eggs acquire the ability to mount the specialized fertilization-specific Ca(2+) signal during oocyte maturation. The first Ca(2+) transient following sperm entry in vertebrate eggs has a slow rising phase followed by a sustained plateau. The molecular determinants of the sustained plateau are poorly understood. We have recently shown that a critical determinant of Ca(2+) signaling differentiation during oocyte maturation is internalization of the plasma membrane calcium ATPase (PMCA). PMCA internalization is representative of endocytosis of several integral membrane proteins during oocyte maturation, a requisite process for early embryogenesis. Here we investigate the mechanisms regulating PMCA internalization. To track PMCA trafficking in live cells we cloned a full-length cDNA of Xenopus PMCA1, and show that GFP-tagged PMCA traffics in a similar fashion to endogenous PMCA. Functional data show that MPF activation during oocyte maturation is required for full PMCA internalization. Pharmacological and co-localization studies argue that PMCA is internalized through a lipid raft endocytic pathway. Deletion analysis reveal a requirement for the N-terminal cytoplasmic domain for efficient internalization. Together these studies define the mechanistic requirements for PMCA internalization during oocyte maturation.
El-Jouni
Wassim
W
Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Haun
Shirley
S
Machaca
Khaled
K
D000595:Amino Acid Sequence; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis; D005260:Female; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D009866:Oogenesis; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology / Q000502:physiology*
D029867:Xenopus Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases