Expression And Significant Of USP2-69 In Mesangial Cell In Glomerulonephritis

To our knowledge,the degradation of ubiquitin-conjugated cellular proteins by the proteasome system plays a key role in many cellular processes,including cell cycle control,DNA repair,regulation of transcription,growth differentiation,receptor function,immune and inflammatory responses,and oncoprotein degradation.This system is also regulated by a reversible process involving many deubiquitination en2ymes,among which the ubiquitin-specific processing proteins2(USP2) is an important member.USP2 exists on chromosome 11q23,form the three isoforms of USP2-41KD,USP2-45KD and USP2-69KD according to different splicing.Recent study found USP2 expression in many adult and embryonic tissues including testis, heart,skeletal muscle,brain,kidney,liver and pancreas.USP2-69 has been found to be an effective regulator of cell growth and differentiation.For example,USP2-69 expression in testis is necessary for spermatogenesis;overexpression of USP2-69 in human prostate cancer promotes tumor growth by directly stabilizing fatty acid synthetase as well as indirectly enhancing p53 degradation by stabilizing Mdm2. USP2-69 expression was seen high in kidney tissue,but its role remains unclear. Mesangial cell proliferation is a key element of various glomerulonephritis.So it is an interesting question worthy of exploration whether USP2-69 is expressed in glomeruli and plays a role in mesangial cell proliferation in glomerulonephritis.In current study,we investigated the expression of USP2-69 in mesangial cells in vivo and vitro.In cultrued mesangial cells,the expression of USP2-69 in normal mesangial cell was detected,then the cells were treated with inflammatory factor IL-1βas well as antithymocyte serum(ATS,could interact with antigens on the cell membrane of MsC to form immunecomplexes) and fresh human serum including complements to form immune injury in vitro.The result showed that USP2-69 and USP2-45 isoforms were constitutively expressed in normal rat MsC;the isoforms of USP2-69 mRNA and protein expression were both elevaed in rat mesangial cells after stimulation by IL-1βand ATS,but the USP2-45 isoform was no changed.Meanwhile, USP2-69 upregulation was accompanied with increasing of PCNA expression and decreasing of p27 expression significantly after stimulation by IL-1βand ATS.So it is indicated that USP2 upexpression maybe related to the cell proliferation in mesangial cells.In order to definite USP2-69 expression in mesangial cell in glomerulonephritis, we futher detected USP2-69 by immunohistochemistry in paraffin-embedded tisssues of kidney needle biopsy from 57 cases containing several glomerulonephritis and healthy kidney tissue(distant from kidney tumour).Immunostaining rerult indicated that USP2-69 was expressed in the capillary tufts of glomeruli,mainly distributed in the mesangial area.In addition,the degree of USP2-69 expression in mesangium of glomeruli was somewhat different among various types of glomerulonephritis. Compared with healthy kidney tissue,the expression level of USP2-69 was markedly higher in acute proliferative glomerulonephritis(APGN),lupus nephritis(LN) and IgA nephropathy(P＜0.05),while little changed in minimal change disease(MCD) and membranous glomerulonephritis(MGN)(P＞0.05).Simultaneously,USP2-69 was widely expressed in tubular epithelial cells and parietal epithelial cells of Bowman's capsules.The distribution of USP2-69 immunostaining was localized mainly in mesangial area in paraffinsection,which is confirmed by PCNA immunoreaction stain in the successive sections of the same biopsies above.Compared with healthy kidney tissue, the positive cell numbers of PCNA was markedly higher in acute proliferative glomerulonephritis(APGN),lupus nephritis(LN) and IgA nephropathy(P＜0.05), while little changed in minimal change disease(MCD) and membranous glomerulonephritis(MGN)(P＞0.05).The uptrend of PCNA expression resembled the patterns of USP2 expression in these renal diseases.Simultaneously,we found that the localizing of PCNA nucleus consisted with the distribution of USP2 positive position in mesangium in some proliferative nephritises such as IgA nephropathy (mesangial proliferative type) and LN(Ⅳ).This data suggessed that USP2 expression in mesangial cells maybe related to the mesangial cell proliferation. In summary,USP2-69 expression was first reported in mesangial cells. Inflammatory factor and immune complex could up-regulation USP2-69 as well as up-regulation PCNA and down-regulation p27.The up-expression of USP2-69 in human glomerulonephritis was closely related to the pathological types.It was exhibited by high expression of USP2-69 in mesangial proliferative glomerulonephritises such as APGN,IgAN and LN.So our result indicated that the potential relationship of up-expression of USP2-69 and mesangial cell proliferation. In general,our work will contribute to understanding the pathogenesis of glomerulonephritis and providing with experimental basis and evidence for the studying of mechanism about USP2-69 regulation mesangial proliferation as well as novel strategies for the treatment of mesangial proliferative glomerulonephritises.