HIV-1 promotes renal tubular epithelial cell protein synthesis: role of mTOR pathway.

Shabina Rehman,Ashwani Malhotra,Mohammad Husain,Pravin C Singhal,Balakuntalam S Kasinath,Anju Yadav

doi:10.1371/journal.pone.0030071

Shabina Rehman, Ashwani Malhotra + Show 4 more

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https://doi.org/10.1371/journal.pone.0030071

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Abstract

Tubular cell HIV-infection has been reported to manifest in the form of cellular hypertrophy and apoptosis. In the present study, we evaluated the role of mammalian target of rapamycin (mTOR) pathway in the HIV induction of tubular cell protein synthesis. Mouse proximal tubular epithelial cells (MPTECs) were transduced with either gag/pol-deleted NL4-3 (HIV/MPTEC) or empty vector (Vector/MPTEC). HIV/MPTEC showed enhanced DNA synthesis when compared with Vector/MPTECs by BRDU labeling studies. HIV/MPTECs also showed enhanced production of β-laminin and fibronection in addition to increased protein content per cell. In in vivo studies, renal cortical sections from HIV transgenic mice and HIVAN patients showed enhanced tubular cell phosphorylation of mTOR. Analysis of mTOR revealed increased expression of phospho (p)-mTOR in HIV/MPTECs when compared to vector/MPTECs. Further downstream analysis of mTOR pathway revealed enhanced phosphorylation of p70S6 kinase and associated diminished phosphorylation of eEF2 (eukaryotic translation elongation factor 2) in HIV/MPTECs; moreover, HIV/MPTECs displayed enhanced phosphorylation of eIF4B (eukaryotic translation initiation factor 4B) and 4EBP-1 (eukaryotic 4E binding protein). To confirm our hypothesis, we evaluated the effect of rapamycin on HIV-induced tubular cell downstream signaling. Rapamycin not only attenuated phosphorylation of p70S6 kinase and associated down stream signaling in HIV/MPTECs but also inhibited HIV-1 induced tubular cell protein synthesis. These findings suggest that mTOR pathway is activated in HIV-induced enhanced tubular cell protein synthesis and contributes to tubular cell hypertrophy.

Highlights

HIV-associated nephropathy (HIVAN) is characterized by tubular microcyst formation [1]
Dilated tubules in both HIVAN patients and Tg26 mice displayed enhanced phospho-mammalian target of rapamycin (mTOR) expression by tubular cells. These findings indicate the activation of mTOR pathway in diseased tubules in HIVAN patients and Tg26 mice
HIV promotes mTOR pathway activation in Tubular cells To determine the activation of mTOR pathway, lysates from vector/Mouse proximal tubular epithelial cells (MPTECs) and HIV/MPTECs were prepared for Western blotting and probed for the expression of proteins molecules involved in the downstream signaling of the mTOR complex1 (mTORC1) pathway (n = 4)

Summary

Introduction

HIV-associated nephropathy (HIVAN) is characterized by tubular microcyst formation [1]. Tubular cells in these lesions display growth arrest, hypetrophy and apoptosis [2]. The role of mTOR has been suggested in the development of renal lesions in a mouse model of HIVAN [7]. In these studies, HIV transgenic mice (Tg26) displayed expression of phosphomTOR by kidney cells. Renal tissues from Tg26 mice displayed enhanced phosphorylation of p70S6 kinase and eEF2K and showed enhanced phosphorylation of 4E-BP-1 and eIF4B; these findings indicated the activation of mTOR pathway in kidney cells of HIV transgenic mice. Since mTORC1 plays an important role in the regulation of mRNA translation, a rate-limiting step in protein synthesis, we hypothesized that HIV-1 recruits mTOR for the induction of tubular cell protein synthesis

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