ACTIVATION OF P56LCK THROUGH MUTATION OF A REGULATORY CARBOXY-TERMINAL TYROSINE RESIDUE REQUIRES INTACT SITES OF AUTOPHOSPHORYLATION AND MYRISTYLATION
ACTIVATION OF P56LCK THROUGH MUTATION OF A REGULATORY CARBOXY-TERMINAL TYROSINE RESIDUE REQUIRES INTACT SITES OF AUTOPHOSPHORYLATION AND MYRISTYLATION
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DOI：
10.1128/mcb.10.10.5197
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发表时间：
1990-10-01
影响因子：
5.3
通讯作者：
VEILLETTE, A
中科院分区：
文献类型：
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作者：
ABRAHAM, N;VEILLETTE, A
将p56 lck体内酪氨酸磷酸化的主要位点（酪氨酸505）突变为苯丙氨酸，组成性地增强了p56 lck相关的酪氨酸特异性蛋白激酶活性。该突变多肽在体外Lck自磷酸化位点（酪氨酸394）在体内被广泛磷酸化，并且能够使啮齿动物成纤维细胞发生致癌转化。这些观察结果表明，在Tyr-505磷酸化下调p56 lck的酪氨酸蛋白激酶活性。在此，我们试图研究是否其他翻译后修饰可能参与调节p56 lck的酶功能。结果表明，酪氨酸-505突变激活p56 lck的阻止酪氨酸-苯丙氨酸取代位置394。此外，激活p56 lck的突变的羧基末端酪氨酸残基，使效率较低的取代氨基末端甘氨酸的丙氨酸残基。这第二个突变阻止p56 lck肉豆蔻基化和稳定的膜assocation，并与减少在体内磷酸化Tyr-394。总之，这些发现意味着缺乏磷酸化的酪氨酸-505可能是不够的增强p56 lck相关的酪氨酸蛋白激酶活性。我们的数据表明，激活p56 lck可能依赖于磷酸化酪氨酸-394，这一过程可能是促进肉豆蔻酰化，膜协会，或两者兼而有之。
Mutation of the major site of in vivo tyrosine phosphorylation of p56lck (tyrosine 505) to a phenylalanine constitutively enhances the p56lck-associated tyrosine-specific protein kinase activity. The mutant polypeptide is extensively phosphorylated in vivo at the site of in vitro Lck autophosphorylation (tyrosine 394) and is capable of oncogenic transformation of rodent fibroblasts. These observations have suggested that phosphorylation at Tyr-505 down regulates the tyrosine protein kinase activity of p56lck. Herein we have attempted to examine whether other posttranslational modifications may be involved in regulation of the enzymatic function of p56lck. The results indicated that activation of p56lck by mutation of Tyr-505 was prevented by a tyrosine-to-phenylalanine substitution at position 394. Furthermore, activation of p56lck by mutation of the carboxy-terminal tyrosine residue was rendered less efficient by substituting an alanine residue for the amino-terminal glycine. This second mutation prevented p56lck myristylation and stable membrane assocation and was associated with decreased in vivo phosphorylation at Tyr-394. Taken together, these findings imply that lack of phosphorylation at Tyr-505 may be insufficient for enhancement of the p56lck-associated tyrosine protein kinase activity. Our data suggest that activation of p56lck may be dependent on phosphorylation at Tyr-394 and that this process may be facilitated by myristylation, membrane association, or both.