SH2 domain-mediated activation of phospholipase Cgamma is not required to initiate Ca2+ release at fertilization of mouse eggs.
SH2 domain-mediated activation of phospholipase Cgamma is not required to initiate Ca2+ release at fertilization of mouse eggs.
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DOI：
10.1006/dbio.1998.9051
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发表时间：
1998-11
影响因子：
2.7
通讯作者：
L. Mehlmann;G. Carpenter;S. Rhee;L. Jaffe
中科院分区：
文献类型：
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作者：
L. Mehlmann;G. Carpenter;S. Rhee;L. Jaffe
哺乳动物卵子受精时Ca2+释放的启动需要三磷酸肌醇(Miyazaki et al., 1992, Science 257, 251-255)，表明磷脂酶C家族的酶可能被激活。由于棘皮动物卵受精时 Ca2+ 的释放是由 SH2 结构域介导的磷脂酶 Cgamma 激活启动的（Carroll et al., 1997, J. Cell Biol. 138, 1303-1311），因此我们研究了 PLCgamma 在小鼠卵受精时启动 Ca2+ 释放中的可能作用。 PLCgamma 两种异构体 PLCgamma1 和 PLCgamma2 均存在于小鼠卵子和精子中，通过外源表达的 PDGF 受体刺激卵子中的这些酶会导致 Ca2+ 释放。 PLCgamma1 和 PLCgamma2 的重组 SH2 结构域可抑制 PDGF 受体对 PLCgamma1 和 PLCgamma2 的激活，当以比内源蛋白浓度高约 20 至 40 倍的剂量注射时，完全阻止 PDGF 引起的 Ca2+ 释放。然而，即使超出内源蛋白水平约 100 至 400 倍，PLCgamma1 和 PLCgamma2 SH2 结构域也不会抑制受精时 Ca2+ 的释放。这些发现表明，小鼠卵子受精时 Ca2+ 的释放不需要 SH2 结构域介导的 PLCgamma 激活。然而，通过替代途径激活卵子中的 PLCgamma，或从精子引入激活的 PLCgamma，可能很重要。
The initiation of Ca2+ release at fertilization of mammalian eggs requires inositol trisphosphate (Miyazaki et al., 1992, Science 257, 251-255), indicating that an enzyme of the phospholipase C family is probably activated. Because Ca2+ release at fertilization in echinoderm eggs is initiated by SH2 domain-mediated activation of phospholipase Cgamma (Carroll et al., 1997, J. Cell Biol. 138, 1303-1311), we examined the possible role of PLCgamma in initiating Ca2+ release at fertilization in mouse eggs. Both PLCgamma isoforms, PLCgamma1 and PLCgamma2, are present in mouse eggs and sperm, and stimulation of these enzymes in the egg by way of an exogenously expressed PDGF receptor causes Ca2+ release. Recombinant SH2 domains of PLCgamma1 and PLCgamma2 inhibit PLCgamma1 and PLCgamma2 activation by the PDGF receptor, completely preventing Ca2+ release in response to PDGF when injected at an approximately 20- to 40-fold excess over the concentrations of endogenous proteins. However, even at an approximately 100- to 400-fold excess over endogenous protein levels, PLCgamma1 and PLCgamma2 SH2 domains do not inhibit Ca2+ release at fertilization. These findings indicate that Ca2+ release at fertilization of mouse eggs does not require SH2-domain-mediated activation of PLCgamma. However, activation of PLCgamma in the egg by an alternative pathway, or introduction of activated PLCgamma from the sperm, may be important.