Kurvari V, Snell W J
Department of Cell Biology and Neuroscience, University of Texas, Southwestern Medical Center, Dallas 75235, USA.
Biochem Biophys Res Commun. 1996 Nov 1;228(1):45-54. doi: 10.1006/bbrc.1996.1614.
Fertilization in the biflagellated eukaryote, Chlamydomonas, is initiated by flagellar adhesion between gametes of opposite mating types. An early event in the signal transduction pathway induced by these cell-cell interactions is the rapid inactivation of a flagellar protein kinase that phosphorylates a 48 kDa flagellar protein. Molecular cloning and characterization indicated that the 48 kDa substrate, termed SksC, itself is a novel protein kinase. Here, we have determined that its transcript levels were unchanged during prolonged flagellar adhesion. Moreover, resynthesis of new flagellar proteins following deflagellation was not accompanied by increases in transcript levels of SksC, suggesting that expression of this soluble protein kinase might not be restricted to flagella. Immunoblot analysis indicated that expression of SksC was ubiquitous: this soluble protein was found in both flagella and cell bodies and was expressed throughout the cell cycle and gametogenesis. Immunoprecipitation experiments indicated that SksC was phosphorylated in both flagella and cell bodies. Thus, in addition to its potential role in fertilization, this novel protein kinase may play a role in other signaling events in Chlamydomonas.
在双鞭毛真核生物衣藻中，受精作用由不同交配型配子之间的鞭毛黏附引发。这些细胞间相互作用所诱导的信号转导途径中的一个早期事件，是一种使48 kDa鞭毛蛋白磷酸化的鞭毛蛋白激酶迅速失活。分子克隆和特性分析表明，这种48 kDa的底物（称为SksC）本身是一种新型蛋白激酶。在此，我们已确定，在长时间的鞭毛黏附过程中其转录水平没有变化。此外，去鞭毛后新鞭毛蛋白的重新合成并未伴随着SksC转录水平的增加，这表明这种可溶性蛋白激酶的表达可能并不局限于鞭毛。免疫印迹分析表明，SksC的表达是普遍存在的：这种可溶性蛋白在鞭毛和细胞体中均有发现，并且在整个细胞周期和配子发生过程中都有表达。免疫沉淀实验表明，SksC在鞭毛和细胞体中均被磷酸化。因此，除了其在受精过程中的潜在作用外，这种新型蛋白激酶可能在衣藻的其他信号事件中发挥作用。
