Expression and function of ADAR1 and PACT and their impact on PKR activation during HIV-1 infection — ASN Events
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  3. Expression and function of ADAR1 and PACT and their impact on PKR activation during HIV-1 infection

Expression and function of ADAR1 and PACT and their impact on PKR activation during HIV-1 infection (#34)

Aïcha Daher 1 , Samantha Burugu 1 2 , Guerline Clerzius 1 3 , Eileen Shaw 1 3 , Roman Radetskyy 1 2 , Jean-Pierre Routy 3 4 , Anne Gatignol 1 2 3
  1. Lady Davis Institute for Medical Research, Montreal, QUE, Canada
  2. Department of Microbiology and Immunology, McGill University, Montreal
  3. Department of Medicine, division of Experimental Medicine, McGill University, Montreal
  4. Division of Hematology, McGill University, Montreal
 

Aims: A poor innate immune response contributes to the establishment of viral latency and persistence in human immunodeficiency virus (HIV)-1 infection. The protein kinase RNA-activated (PKR) is an Interferon-stimulated gene (ISG) that senses RNA viruses. PKR is a potent HIV-1 suppressor through the phosphorylation of the translation initiation factor eIF2α and consequent inhibition of protein synthesis. We showed that PKR is activated at the beginning of HIV-1 infection followed by a deactivation due, in part, to cellular proteins TRBP and ADAR1. Although PACT is a PKR activator, we showed that it becomes a PKR inhibitor in HIV-expressing cells (1). Our hypothesis is that PKR inhibition contributes to HIV-1 replication and persistence through multiple mechanisms. Our objective is to elucidate how ADAR1 and PACT contribute to PKR inhibition during HIV-1 infection.

 Methods: We analysed the expression of PKR, ADAR1 and PACT in HIV-infected patients and in peripheral blood mononuclear cells (PBMCs) infected with HIV-1 by western blots and immunoprecipitations. We used short hairpin (sh)RNAs against ADAR1 and PACT to assess their impact on HIV-1 production. We assessed the interaction between ADAR1 and PACT and its impact on PACT function.

Results: ADAR1 and PACT expression are increased in HIV-1 infected PBMCs and immunoprecipitate with PKR. This is correlated with PKR deactivation and increased viral expression. A decrease of either ADAR1 or PACT inhibits HIV-1 production. A direct interaction between ADAR1 and PACT suggests a functional significance on PACT and PKR functions during HIV replication.

Conclusion: The increased expression of both ADAR1 and PACT contribute to PKR inhibition in HIV-1 infected cells. PACT changes its function for a PKR inhibitor in HIV-infected cells, which could be due to its interaction with ADAR1, thereby contributing to viral persistence in patients.  

(1) Clerzius et al., 2013, Retrovirology, 10:96