The ROCO Kinase QkgA Is Necessary for Proliferation Inhibition by Autocrine Signals in Dictyostelium discoideum
The ROCO Kinase QkgA Is Necessary for Proliferation Inhibition by Autocrine Signals in Dictyostelium discoideum
复制标题
DOI：
10.1128/ec.00121-10
复制
发表时间：
2010-10-01
期刊：
影响因子：
--
通讯作者：
Gomer, Richard H.
中科院分区：
文献类型：
--
作者：
Phillips, Jonathan E.;Gomer, Richard H.
AprA 和 CfaD 是分泌蛋白，作为自分泌信号抑制盘基网柄菌细胞增殖。缺乏 AprA 或 CfaD 的细胞增殖迅速，而向细胞添加 AprA 或 CfaD 则增殖减慢。缺乏ROCO激酶QkgA的细胞增殖迅速，倍增时间是野生型的83%，而QkgA-绿色荧光蛋白(GFP)融合蛋白的过度表达会减慢细胞增殖。我们发现qkgA(-)细胞积累正常水平的细胞外AprA和CfaD。外源性 AprA 或 CfaD 不会减缓缺乏 qkgA 的细胞的增殖，而 qkgA(-) 细胞中 QkgA-GFP 的表达可以挽救这种不敏感性。与缺乏 AprA 或 CfaD 的细胞一样，缺乏 QkgA 的细胞往往是多核的，细胞核快速积累，并且每个核显示出与野生型相同的质量和蛋白质积累，表明 QkgA 负向调节增殖，但不负向调节生长。尽管缺乏 AprA、CfaD 或 QkgA 的细胞增殖速度很快，但它们在细菌上形成菌落时的扩张速度却慢于野生型。与 AprA 和 CfaD 不同，QkgA 不会影响多细胞发育后的孢子活力。总之，这些结果表明 QkgA 对于 AprA 和 CfaD 的增殖抑制是必需的，QkgA 介导 AprA 和 CfaD 的部分但不是全部作用，并且 QkgA 可能在调节增殖的信号转导途径中发挥作用。
AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA(-) cells accumulate normal levels of extracellular AprA and CfaD. Exogenous AprA or CfaD does not slow the proliferation of cells lacking qkgA, and expression of QkgA-GFP in qkgA(-) cells rescues this insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend to be multinucleate, accumulate nuclei rapidly, and show a mass and protein accumulation per nucleus like those of the wild type, suggesting that QkgA negatively regulates proliferation but not growth. Despite their rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a colony on bacteria less rapidly than the wild type. Unlike AprA and CfaD, QkgA does not affect spore viability following multicellular development. Together, these results indicate that QkgA is necessary for proliferation inhibition by AprA and CfaD, that QkgA mediates some but not all of the effects of AprA and CfaD, and that QkgA may function downstream of these proteins in a signal transduction pathway regulating proliferation.