Study The Biological Function Of Tyrosine/dual-specificity Phosphatase MTM-5 In C.elegans

Both protein tyrosine phosphatases and protein tyrosine kinases regulatethe phosphorylation of the protein tyrosine residues, the phosphorylation oftyrosine is correlated with the human health and diseases strongly, such as cellsignaling transduction, morph, motility, cell division and proliferation, theregulation of gene transcription and the transportation of molecule, these areall related to the tyrosine phosphorylation, Moreover, the tyrosinephosphorylation also plays an important role in embryogenesis, allelotaxy,histological differentiation, and the immune defense.The PTPs family consists of a large number of members, classical PTPs,such as PTP1B is tyrosine specific, and the "dual-specific" proteinphosphatases (DSPs) can dephosphorylate the phosphorylated proteins. MTMfamily belongs to the PTP/DSPs family, whose members almost exist in all theeukaryocytes, including Saccharomyces siccum and the plants. Recently, acatalytically active and an inactive member of the myotubularins family(MTMR2 and MTMR13/Sbf2 respectively) have been identified as mutated intwo demyelinating recessive forms of CMT type 4B (CMT4B)1 and 2, and themutation of MTMR2 MTMR13/Sbf1 also leads to the defect of gonepoiesisand spermacrasia. These ubiquitously expressed myotubularins are thusimplicated in diseases affecting different tissues. The myotubularin familyencompasses catalytically active and inactive phosphatases. Surprisingly,recent data suggest that there is a functional cooperation between members ofthese two classes.The myotubularin family contains 14 genes in human, named MTM1 andMTMRelated 1 to 13, and at least two pseudogenes. In Metazoa, it can bedivided into six subgroups, each with one member in Caenorhabditis elegansand Drosophila melanogaster. They all share homologies with the active site oftyrosine and dualspecificity phosphatases, which can dephosphorylate thephosphoinositide and dephosphorylate PI3P , Thus myotubularins couldrepresent a fourth type of regulator of endosome trafficking bydephosphorylating PI3P. The hypothesis that catalytically inactivephosphatases could regulate phosphorylation level by cooperating with activephosphatases is a new concept and brings a third player into the opposingcouple kinase/phosphatase.MTMs related diseases are Myotubular myopathy (XLMTM) andCharcot–Marie–Tooth (CMT). Myotubular myopathy (XLMTM) is a usuallyvery severe congenital myopathy associated with major hypotonia at birth. TheMtm1 knockout mice recapitulate the histopathological signs of XLMTM andshow a progressive myopathy starting a few weeks after birth while musclehistology appears normal at birth. This suggests that the disorganizedappearance of the muscle fibers is due to a defect in structural maintenancerather than an impairment in myogenesis as previously hypothesized.Charcot–Marie–Tooth (CMT) disease is the most frequent class of inheriteddisorder of the peripheral nervous system and is classified into demyelinatingand axonal neuropathies.C.elegans is a perfect experiment living model and RNAi carrier withshort lifespan. It is easy to feed and its transparent epidermis can ease theprocess of observation. More importantly, it is a eucaryotic metazoan whosecells, molecular constructions and regulation passways are correspondent withhigher animals. All these above unique advantages make C.elegans as anexcellent model organism.The members of MTMs family, MTM-1, MTM-3, MTM-5, MTM-6 andMTM-9, have been discovered in nematode, and some of them functionsduring the cell endocytosis. We mainly study the function of MTM-5 innematode C.elegans, mtm -5 gene locates in the X chromosome,5243354-5234662bp. PH, DENN, GRAM and C1 domains construct theMTM-5 protein, Its function is unknown now,It is confirmed that it correlateswith some cell signal cascade and dephosphorylates some cyclohexanhexoland monophosphoinositide.Previous study suggests that MTMs correlated with human diseases, weuse mtm-5 gene knockout C.elegans named VC263 as model to test the bodylength, lifespan, locomotion, pharynx pumping, defection interval, egg layingand so on, and construct some integrated and accurate methods for phenotypeobservation.We compare the phenotype between the mtm-5 gene knockout group andthe control group, the results show that the body shape of mtm-5 knockoutnematodes differs from the control. The lifespan of VC263 is shorter thancontrol, This may imply the lifespan of VC263 has relationship with negativeregulation of phosphoinositide level. At the same time, PTEN/daf-18 andMTM-5 belong to the same family, and PTEN/daf-18 can also regulate thephosphoinositide level negtively, result in downstream target daf-16 enters intonucleus, then improves the expression level of heat shock factor andantioxidant enzyme gene to delay aging, this suggests MTM-5 may be anegative regulator of phosphoinositide level in the insulin growth factorsignaling pathway to influence the nematode lifespan. The locomotion ofmtm-5 gene knockout group is obviously faster than control group, thissuggests that MTM-5 also plays a negative regulation role in the muscledevelopment. We study the biological function of mtm-5 gene in thisexperiment preliminary, the results may provide rationale for the study ofMTM family enzymes and the MTMs regulation mechanism, it can alsoprovide a target for new drug of related diseases.