Atıcı Sena, Çizmecioğlu Onur
Department of Molecular Biology and Genetics, Bilkent University Faculty of Medicine, Ankara, Turkey.
Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany.
J Turk Ger Gynecol Assoc. 2024 Aug 29;25(3):159-166. doi: 10.4274/jtgga.galenos.2024.2024-6-7.
The phosphoinositide 3-kinase (PI3K) pathway is an important signaling mechanism for cell proliferation and metabolism. Mutations that activate PIK3CA may make cells p110α dependent, but when phosphatase tensin homolog (PTEN) is lost, the p110β isoform of PI3Ks becomes more important. However, the exact mechanism underlying the prevalence of p110s remains unclear. In this study, our aim was to elucidate the processes behind PI3K isoform dependency in a cellular model of embryonic development.
In order to understand PI3K isoform prevalence, mouse embryonic fibroblasts (MEFs) were used and p110β, PTEN and Rac1 activity was modulated using retroviral plasmids. Expression levels and cellular growth were assessed by performing immunoblots and crystal violet assays.
The levels of PTEN had only a partial effect on the prevalence of PI3K isoforms in MEFs. The dependency on p110α diminished when PTEN was depleted. Of note, when PTEN expression was repressed, there was no full transition in dependency from one PI3K isoform to the other. Interestingly, the viability of PTEN-depleted MEFs became less dependent on p110α and more dependent on p110β when p110β was overexpressed. Nevertheless, the overexpression of p110β in conjunction with PTEN knock-downs did not result in a complete shift of isoforms in PI3Ks. Finally, we investigated Rac1 activation with a mutant allele and determined a more potent increase in p110β prominence in MEFs.
These findings suggest that multiple cellular parameters, including PTEN status, PI3K isoform levels, and Rac1 activity, combine to influence PI3K isoform prevalence, rather than a single determinant.
磷酸肌醇3-激酶（PI3K）信号通路是细胞增殖和代谢的重要信号机制。激活PIK3CA的突变可能使细胞对p110α产生依赖性，但当张力蛋白同源磷酸酶（PTEN）缺失时，PI3K的p110β亚型变得更为重要。然而，p110s普遍存在的确切机制仍不清楚。在本研究中，我们的目的是在胚胎发育的细胞模型中阐明PI3K亚型依赖性背后的过程。
为了了解PI3K亚型的普遍情况，使用了小鼠胚胎成纤维细胞（MEF），并通过逆转录病毒质粒调节p110β、PTEN和Rac1的活性。通过免疫印迹和结晶紫测定评估表达水平和细胞生长。
PTEN的水平对MEF中PI3K亚型的普遍情况只有部分影响。当PTEN被耗尽时，对p110α的依赖性降低。值得注意的是，当PTEN表达受到抑制时，依赖性并没有从一种PI3K亚型完全转变为另一种。有趣的是，当p110β过表达时，PTEN缺失的MEF的活力对p110α的依赖性降低，而对p110β的依赖性增加。然而，p110β的过表达与PTEN的敲低相结合并没有导致PI3K中亚型的完全转变。最后，我们用突变等位基因研究了Rac1的激活，并确定了MEF中p110β突出性的更有效增加。
这些发现表明，包括PTEN状态、PI3K亚型水平和Rac1活性在内的多个细胞参数共同影响PI3K亚型的普遍情况，而不是单一决定因素。
