Fertilization and inositol 1,4,5-trisphosphate (IP3)-induced calcium release in type-1 inositol 1,4,5-trisphosphate receptor down-regulated bovine eggs.
It is widely believed that stimulation of the phosphoinositide pathway and production of 1,4,5-inositol trisphosphate (IP(3)) underlies the oscillatory changes in the concentration of intracellular free calcium ions ([Ca(2+)](i)) seen during mammalian fertilization. IP(3) promotes Ca(2+) release in eggs by binding to its receptor, the type-1 IP(3) receptor (IP(3)R-1, also known as ITPR1), a ligand-gated Ca(2+) channel located in the membrane of the endoplasmic reticulum, the main Ca(2+) store of the cell. While IP(3)R-1 has been shown to mediate all Ca(2+) release during mouse fertilization, whether or not it plays such an essential role in fertilization-induced Ca(2+) release in large domestic species such as bovine and porcine is presently not known. Accordingly, we have generated metaphase II bovine eggs with a approximately 70%-80% reduction in the number of intact IP(3)R-1 by inducing receptor down-regulation during oocyte maturation. We did so by injecting the nonhydrolyzable IP(3) analogue, adenophostin A. Functional Ca(2+) release analysis revealed that IP(3)R-1 is the predominant Ca(2+) release channel in bovine eggs, requiring as little as 20% of total intact receptor to mount persistent [Ca(2+)](i) oscillations in response to fertilization, expression of PLCzeta (also known as PLCZ1), and adenophostin A. However, lower concentrations of IP(3) and near-physiological concentrations of porcine sperm extract were unable to trigger [Ca(2+)](i) oscillations in this reduced IP(3)R-1 model. Furthermore, we present evidence that the sensitivity of bovine IP(3)R-1 is impaired at the first embryonic interphase. Together, these results demonstrate the essential role of IP(3)R-1-mediated Ca(2+) release during fertilization in bovine eggs, and identify cell cycle regulatory mechanisms of [Ca(2+)](i) oscillations at the level of IP(3)R-1.
Malcuit
Christopher
C
Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, 01003, USA.
Knott
Jason G
JG
He
Changli
C
Wainwright
Tara
T
Parys
Jan B
JB
Robl
James M
JM
Fissore
Rafael A
RA
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002417:Cattle / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D015536:Down-Regulation; D005260:Female; D005306:Fertilization / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D051379:Mice; D009865:Oocytes / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013552:Swine
D002120:Calcium Channel Agonists; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; C085029:adenophostin A; D015544:Inositol 1,4,5-Trisphosphate; D000241:Adenosine; D002118:Calcium