The Study Of Disulfides Regulating Structure,Function And Cellular Distribution Of Galectin-13

Preeclampsia,also known as eclampsia,is a serious maternal and infant complication.After 20 weeks of gestation,the patients have high blood pressure,proteinuria,edema and other symptoms.Severe patients can even have headache,dizziness,nausea and vomiting.The cause of the disease is still unclear.At present,there is no effective treatment except termination of pregnancy.Studies on the causes of eclampsia have found that during pregnancy,Galectin-13,also known as Placental protein 13(PP13),is highly expressed in syncytiotrophoblast cells of the placenta,and its low expression level or mutation will lead to eclampsia,but many complex internal mechanisms are still unclear.As we all know,structure determines function,there is a special structure in Galectin-13-disulfide bond.Currently,there are few studies on Galectin-13 disulfide bond.Therefore,in-depth study of Galectin-13 and its mutants is crucial to find a way to control the normal expression of Galectin-13 and to explore an effective treatment for eclampsia.Previous data on crystal structure and Gel filtration showed that Galectin-13 formed two disulfide bonds via Cys136 and Cys138,forming a dimer.In this study,we mutated two cysteine to serine to form three mutants C136 S,C138S and C136S/C138 S,and crystallized the three mutants and solved their crystal structure.The crystal structure showed that all mutants crystallize as monomers.In the structure of C136 s,Cys138 and Cys19 formed disulfide bond,which indicated that Cys19 played an important role in regulating the reversible disulfide bond formation of the lectin.Although Gel filtration results showed that some C136 S and C138 S could form two dimers,however,Hemagglutination tests showed that none of the mutants could induce erythrocyte agglutination,indicating that these two polymers did not exhibit the same activity as wild type Galectin-13.In HeLa cells,the proteins of three mutants are the same as wild type Galectin-13,which are mainly distributed in the nucleus and may be involved in the regulation of DNA replication and RNA transcription and other important life processes.In addition,considering the high concentration of reduced glutathione in the cell,wild-type Galectin-13 should exist in the cytoplasm in the form of monomer,which is consistent with the distribution of three mutants in the cell,while another truncated variant of Galectin-13,del221 t,can not enter the nucleus,which can well explain why women with such variation will get preeclampsia.