Role of RIPK1 in SMAC mimetics-induced apoptosis in primary human HIV-infected macrophages

Ramon Edwin Caballero,Simon Xin Min Dong,Michel J Tremblay,Edana Cassol,Ashok Kumar,William D Cameron,Jonathan B Angel,Hamza Ali,Robert Korneluk,Niranjala Gajanayaka

doi:10.1038/s41598-021-02146-w

Abstract

Macrophages serve as viral reservoirs due to their resistance to apoptosis and HIV-cytopathic effects. We have previously shown that inhibitor of apoptosis proteins (IAPs) confer resistance to HIV-Vpr-induced apoptosis in normal macrophages. Herein, we show that second mitochondrial activator of caspases (SMAC) mimetics (SM) induce apoptosis of monocyte-derived macrophages (MDMs) infected in vitro with a R5-tropic laboratory strain expressing heat stable antigen, chronically infected U1 cells, and ex-vivo derived MDMs from HIV-infected individuals. To understand the mechanism governing SM-induced cell death, we show that SM-induced cell death of primary HIV-infected macrophages was independent of the acquisition of M1 phenotype following HIV infection of macrophages. Instead, SM-induced cell death was found to be mediated by IAPs as downregulation of IAPs by siRNAs induced cell death of HIV-infected macrophages. Moreover, HIV infection caused receptor interacting protein kinase-1 (RIPK1) degradation which in concert with IAP1/2 downregulation following SM treatment may result in apoptosis of macrophages. Altogether, our results show that SM selectively induce apoptosis in primary human macrophages infected in vitro with HIV possibly through RIPK1. Moreover, modulation of the IAP pathways may be a potential strategy for selective killing of HIV-infected macrophages in vivo.

Highlights

Macrophages are permissive to productive infection with HIV and a source of viral progeny for transmission to other cell types such as T cells[1,2,3,4]
We have previously shown that the cIAP1/2 play a protective role in mediating survival of macrophages in response to Vpr-induced cell death[35,36,37]
We show that cIAP1/2 are dispensable host factors for the viability of macrophages, these anti-apoptotic proteins play a critical role in the survival of HIV-infected macrophages

Summary

Introduction

Macrophages are permissive to productive infection with HIV and a source of viral progeny for transmission to other cell types such as T cells[1,2,3,4]. To devise strategies to eliminate HIV-infected macrophages, it is imperative to identify apoptosis-related genes and signaling proteins involved in resistance of HIV-infected macrophages to apoptosis. The mechanism underlying this resistance may be related to the differential expression of pro- and anti-apoptotic genes including cIAP proteins. Strategies based on suppressing IAPs by employing SMs, may be useful in killing HIV-infected macrophages. We show that SMs induced apoptosis in in vitro HIV-infected macrophages and that this killing may occur through the concomitant down regulation of both IAPs and receptor interacting protein kinase-1 (RIPK1)

Methods

Results

Conclusion