Bement W M, Capco D G
Department of Zoology, Arizona State University, Tempe 85287-1501.
Proc Natl Acad Sci U S A. 1991 Jun 15;88(12):5172-6. doi: 10.1073/pnas.88.12.5172.
Transit from M phase into interphase in many eukaryotic cells is preceded by an increase in intracellular free calcium ([Ca2+]i), which may act via calcium-dependent enzymes to trigger the M-phase/interphase transition. To test the role of the calcium- and phospholipid-dependent enzyme protein kinase C (PKC) in the M-phase/interphase transition, PKC was activated in M-phase-arrested Xenopus eggs by treatment with the phorbol ester phorbol 12-myristate 13-acetate under conditions that prevent a rise in [Ca2+]i and activation of other calcium-dependent enzymes. Under these conditions, several cellular events characteristic of transit into interphase occur: sperm chromatin decondenses, the Golgi and the nuclear envelope reassemble, and endocytosis resumes. These events are also triggered by treatment of eggs with the diacylglycerol 1,2-dioctanoyl-sn-glycerol. Surprisingly, the activity of M-phase-promoting factor (MPF), a universal regulator of M phase, remains high under these conditions. If [Ca2+]i is subsequently raised, MPF activity is rapidly destroyed. Similarly, lysates made from eggs treated with phorbol 12-myristate 13-acetate support sperm chromatin decondensation in vitro and yet retain high MPF activity, measured either as the ability to induce meiotic resumption in oocytes or as histone H1 kinase activity. These effects are not triggered by the 4 alpha-phorbol ester isomer, which does not activate PKC, and are sensitive to the PKC "pseudosubstrate" peptide. The results suggest that two, parallel signals are generated by the rise in [Ca2+]i both of which contribute to cell cycle regulation. One pathway inactivates MPF; the other pathway activates PKC.
在许多真核细胞中，从M期进入间期之前，细胞内游离钙（[Ca2+]i）会增加，这可能通过钙依赖性酶起作用，从而触发M期/间期转换。为了测试钙和磷脂依赖性酶蛋白激酶C（PKC）在M期/间期转换中的作用，在防止[Ca2+]i升高和其他钙依赖性酶激活的条件下，用佛波酯佛波醇12-肉豆蔻酸酯13-乙酸酯处理处于M期阻滞的非洲爪蟾卵，从而激活PKC。在这些条件下，会发生一些进入间期所特有的细胞事件：精子染色质解聚、高尔基体和核膜重新组装，以及内吞作用恢复。用二酰基甘油1,2-二辛酰-sn-甘油处理卵也会触发这些事件。令人惊讶的是，M期促进因子（MPF）作为M期的通用调节因子，在这些条件下活性仍然很高。如果随后升高[Ca2+]i，MPF活性会迅速被破坏。同样，用佛波醇12-肉豆蔻酸酯13-乙酸酯处理的卵制成的裂解物在体外支持精子染色质解聚，但仍保留高MPF活性，这可以通过诱导卵母细胞减数分裂恢复的能力或组蛋白H1激酶活性来衡量。这些效应不会由不激活PKC的4α-佛波酯异构体触发，并且对PKC“假底物”肽敏感。结果表明，[Ca2+]i升高产生了两个平行信号，这两个信号都有助于细胞周期调控。一条途径使MPF失活；另一条途径激活PKC。
