Study On The Regulatory Role Of CPTEN In C.elegans Aging By Using RNAi

Protein phosphorylation is controlled by the coordinate action of protein kinases and phosphatases and involves in many human diseases such as diabetes, leukaemia, cancers and immunodeficiency, therefore studying on PTPs has been more and more important.PTEN, a kind of cancer suppressor gene, is a dual specificity phosphatases. The PTEN N-terminal contains the enzymatic side with the critical I/VHCXAG- XXRS/TG motif, found in tyrosine phosphatases and dual specificity phosphatases. Analysis of the crystal structure revealed that the PTEN phosphatase domain, although similar to those of other protein phosphatases, has a slightly larger active site. This enlarged active site allows for the accessibility of phospholipid substrates, thereby making PTEN a unique phosphatase. Indeed, phosphatidylinositol 3,4,5-triphosphate (PIP3), rather than phosphoproteins, is the main biologically relevant substrate of PTEN. PIP3 is the major activator of the cell survival kinase Akt. PTEN negatively regulates the AKT/PI3K pathway, one of the most important pathways for cell growth, proliferation, and survival. PTEN indirectly inactivates Akt kinase, the downstream effector of PI3K by dephos- phorylation of PIP3 at the D3 position.Although the negative regulatory role of PTEN in the AKT/PI3K pathway is well established, PTEN may infl uence other cellular functions. PTEN has been shown to associate with and to dephosphorylate focal adhesion kinase (FAK), and thus, proposed to regulate focal adhesion structure, cell migration, and cell invasion by controlling FAK activity. PTEN has also been proposed to modulate the mitogen-activated kinase (MAPK) pathway in several ways. PTEN has been shown to dephosphorylate adaptor protein Shc, resulting in down-regulation of Grb2 and ultimately, MAPK.PTEN is one of the most common targets for mutation in sporadic human cancers, with a mutational frequency rivaling that of p53. PTEN mutations can be detected in at least 20% of primary glioblastomas, particularly those that were high-grade. PTEN is the most frequently mutated gene in prostate cancer. PTEN is also the most frequently mutated gene in endometrial cancer, particularly the endometrioid type. The reported mutational inactivation of PTEN ranges from 33– 83% in both low-grade as well as high-grade endometrioid endometrial cancers and 20–55% in endometrial hyperplasia, suggesting that PTEN is involved in the initial stages of tumor development. Mutations of PTEN are seen in approximately 10% of primary melanomas . Occasionally, PTEN mutations have been reported in sporadic breast cancer (5%), thyroid cancer (7%), head and neck cancer (12%), renal cell carcinoma (6%), lung cancer (9%), lymphoma (5%), hepatocellular carcinoma(6%), and ovarian cancer (9%).PTEN is crucial for developmental processes and may very well be involved in aging and senescence. Elucidating novel substrates of PTEN and the regulators that control PTEN expression will have important clinical implications.RNA interference (RNAi) has undergone a rapid development as a powerful method to the research of Gene Therapy and the Functional Genomics since its discovery by Fire etc. in 1998. It triggers different types of gene silencing by recognition and ultimately the cleavage or translational repression of complementary single-stranded RNAs such as mRNA, and leads to post-transcriptional gene silencing.C.elegans is a perfect RNAi carrier with short lifespan. It is easy to feed and its transparent epidermis can ease the process of observation. More important, it is a eucaryotic metazoan whose cells, molecular constructions and regulating pathways are correspondent with higher animals. All these above unique advantages make C.elegans an excellent model organism.In our research, we studied the biological function of cPTEN, the C.elegans homologue of PTEN using RNAi technique. From the comparison of the physiological phenotypes between RNAi groups and Control groups, we found firstly, there was no significant difference in brood size between the two groups, implicating that loss-function of cPTEN probably has no influence on the reproductive system. Secondly, the ability of movement of interfered TJ1052 was less strong than TJ1052, which revealed that loss-function of cPTEN might result in deficiency of locomotor system and/or pathological changes in related tissues. Thirdly, the results of lifespan assay showed that the lifespans of both interfered groups were significantly shorter than N2, TJ1052 controls, suggesting that cPTEN plays an important role in regulating C.elegans lifespan, and antagonizes AGE-1/PIP3 pathway.The measurements of SOD activity, MDA level and fat accumulation showed that interfered N2 and TJ1052 C.elegans display decreased SOD activity, higher MDA products and lower fat accumulation revealing the aging mechanism regulated by AGE-1/PIP3/cPTEN pathway.Through the above experiments, we primarily explore the biological function of cPTEN protein by interfering C.elegans and analyzing the phenotypes after RNAi. We expect that our study on C.elegans cPTEN will contribute to further investigation into the mechanism of cPTEN and provide an interrelated theory for the drug selection and therapy of PTEN related human diseases.