HIV-1 expression induces cyclin D(1) expression and pRb phosphorylation in infected podocytes: cell-cycle mechanisms contributing to the proliferative phenotype in HIV-associated nephropathy

BACKGROUND: The aberrant cell-cycle progression of HIV-1-infected kidney cells plays a major role in the pathogenesis of HIV-associated nephropathy, however the mechanisms whereby HIV-1 induces infected glomerular podocytes or infected tubular epithelium to exit quiescence are largely unknown. Here, we ask whether the expression of HIV-1 genes in infected podocytes induces cyclin D(1) and phospho-pRb (Ser780) expression, hallmarks of cyclin D1-mediated G(1) → S phase progression. RESULTS: We assessed cyclin D(1) and phospho-pRb (Ser780) expression in two well-characterized models of HIV-associated nephropathy pathogenesis: HIV-1 infection of cultured podocytes and HIV-1 transgenic mice (Tg26). Compared to controls, cultured podocytes expressing HIV-1 genes, and podocytes and tubular epithelium from hyperplastic nephrons in Tg26 kidneys, had increased levels of phospho-pRb (Ser780), a target of active cyclin D(1)/cyclin-dependent kinase-4/6 known to promote G(1) → S phase progression. HIV-1-infected podocytes showed markedly elevated cyclin D(1) mRNA and cyclin D(1) protein, the latter of which did not down-regulate during cell-cell contact or differentiation, suggesting post-transcriptional stabilization of cyclin D(1) protein levels by HIV-1. The selective suppression of HIV-1 transcription by the cyclin-dependent kinase inhibitor, flavopiridol, abrogated cyclin D(1) expression, underlying the requirement for HIV-1 encoded products to induce cyclin D(1). Indeed, HIV-1 virus deleted of nef failed to induce cyclin D(1) mRNA to the level of other single gene mutant viruses. CONCLUSIONS: HIV-1 expression induces cyclin D(1) and phospho-pRb (Ser780) expression in infected podocytes, suggesting that HIV-1 activates cyclin D1-dependent cell-cycle mechanisms to promote proliferation of infected renal epithelium

Podocan, a Novel Small Leucine-rich Repeat Protein Expressed in the Sclerotic Glomerular Lesion of Experimental HIV-associated Nephropathy

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実験腎炎で熱ショック蛋白47(HSP47)の発現が増加し, HSP47のアンチセンスでコラーゲンの蓄積が抑制された

京都大学0048新制・課程博士博士(医学)甲第7518号医博第2049号新制||医||700(附属図書館)UT51-98-W262京都大学大学院医学研究科内科系専攻(主査)教授 藤田 潤, 教授 中尾 一和, 教授 北 徹学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Critical role for Nef in HIV-1-induced podocyte dedifferentiation

Critical role for Nef in HIV-1–induced podocyte dedifferentiation. The notable glomerular feature of human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) is the collapse of the capillary tuft with marked glomerular epithelial cell hyperplasia. These data suggest a loss of normal podocyte function, which is associated with a loss of the podocyte differentiation markers, Wilm's tumor (WT-1), synaptopodin, podocalyxin, and common acute lymphoblastic leukemia antigen (CALLA). We have previously shown that HIV-1 expression can induce these changes in HIV-1 transgenic mice. To identify which HIV-1 gene product(s) are responsible for the phenotypic changes in podocytes, we created multiple mutated HIV-1 constructs and then pseudotyped them with vesticular stomatitis virus glycoprotein (VSVG) envelope to enhance the tropism of these mutant viruses. In addition to gag/pol, the mutant viruses lacked one of the following, env, nef, rev, vif, vpr, or vpu. In addition, we generated single gene expressing pseudotyped viruses to complement the scanning mutation approach of our viral parental construct. Murine podocytes were then infected with one of the viral constructs either lacking or expressing the various HIV-1 genes. We found that HIV-1 nef was necessary and sufficient for proliferation of podocytes and down-regulation of synaptopodin and CALLA. These data suggest that Nef induces many of the changes we observe in HIV transgenic model and, as a result, this now defines the pathway for exploration of host responses to HIV-1 infection