Deady Lylah D, Sun Jianjun
Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, United States of America.
Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, United States of America; Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, United States of America.
PLoS Genet. 2015 Oct 16;11(10):e1005604. doi: 10.1371/journal.pgen.1005604. eCollection 2015 Oct.
Ovulation is essential for the propagation of the species and involves a proteolytic degradation of the follicle wall for the release of the fertilizable oocyte. However, the precise mechanisms for regulating these proteolytic events are largely unknown. Work from our lab and others have shown that there are several parallels between Drosophila and mammalian ovulation at both the cellular and molecular levels. During ovulation in Drosophila, posterior follicle cells surrounding a mature oocyte are selectively degraded and the residual follicle cells remain in the ovary to form a corpus luteum after follicle rupture. Like in mammals, this rupturing process also depends on matrix metalloproteinase 2 (Mmp2) activity localized at the posterior end of mature follicles, where oocytes exit. In the present study, we show that Mmp2 activity is regulated by the octopaminergic signaling in mature follicle cells. Exogenous octopamine (OA; equivalent to norepinephrine, NE) is sufficient to induce follicle rupture when isolated mature follicles are cultured ex vivo, in the absence of the oviduct or ovarian muscle sheath. Knocking down the alpha-like adrenergic receptor Oamb (Octoampine receptor in mushroom bodies) in mature follicle cells prevents OA-induced follicle rupture ex vivo and ovulation in vivo. We also show that follicular OA-Oamb signaling induces Mmp2 enzymatic activation but not Mmp2 protein expression, likely via intracellular Ca2+ as the second messenger. Our work develops a novel ex vivo follicle rupture assay and demonstrates the role for follicular adrenergic signaling in Mmp2 activation and ovulation in Drosophila, which is likely conserved in other species.
排卵对于物种繁衍至关重要,涉及卵泡壁的蛋白水解降解以释放可受精的卵母细胞。然而,调节这些蛋白水解事件的精确机制在很大程度上尚不清楚。我们实验室及其他研究的工作表明,果蝇和哺乳动物排卵在细胞和分子水平上存在若干相似之处。在果蝇排卵过程中,围绕成熟卵母细胞的后部卵泡细胞被选择性降解,卵泡破裂后,残留的卵泡细胞留在卵巢中形成黄体。与哺乳动物一样,这个破裂过程也依赖于定位在成熟卵泡后端(卵母细胞排出的部位)的基质金属蛋白酶2(Mmp2)的活性。在本研究中,我们表明Mmp2的活性受成熟卵泡细胞中章鱼胺能信号通路的调节。当离体培养分离的成熟卵泡时,在没有输卵管或卵巢肌鞘的情况下,外源性章鱼胺(OA;相当于去甲肾上腺素,NE)足以诱导卵泡破裂。敲低成熟卵泡细胞中的α样肾上腺素能受体Oamb(蘑菇体中的章鱼胺受体)可阻止离体OA诱导的卵泡破裂和体内排卵。我们还表明,卵泡OA - Oamb信号通路诱导Mmp2酶激活,但不诱导Mmp2蛋白表达,可能是通过细胞内Ca2+作为第二信使。我们的工作开发了一种新型的离体卵泡破裂试验,并证明了卵泡肾上腺素能信号在果蝇Mmp2激活和排卵中的作用,这在其他物种中可能是保守的。