Active cAMP-dependent Protein Kinase Incorporated within Highly Purified HIV-1 Particles Is Required for Viral Infectivity and Interacts with Viral Capsid Protein

Abstract

Host cell components, including protein kinases such as ERK-2/mitogen-activated protein kinase, incorporated within human immunodeficiency virus type 1 (HIV-1) virions play a pivotal role in the ability of HIV to infect and replicate in permissive cells. The present work provides evidence that the catalytic subunit of cAMP-dependent protein kinase (C-PKA) is packaged within HIV-1 virions as demonstrated using purified subtilisin-digested viral particles. Virus-associated C-PKA was shown to be enzymatically active and able to phosphorylate synthetic substrate in vitro. Suppression of virion-associated C-PKA activity by specific synthetic inhibitor had no apparent effect on viral precursor maturation and virus assembly. However, virus-associated C-PKA activity was demonstrated to regulate HIV-1 infectivity as assessed by single round infection assays performed by using viruses produced from cells expressing an inactive form of C-PKA. In addition, virus-associated C-PKA was found to co-precipitate with and to phosphorylate the CAp24 gag protein. Altogether our results indicate that virus-associated C-PKA regulates HIV-1 infectivity, possibly by catalyzing phosphorylation of the viral CAp24 gag protein.

Mice with Disrupted Type I Protein Kinase A Anchoring in T Cells Resist Retrovirus-Induced Immunodeficiency

“…This is indeed the case in HIV infection, where activation of the cAMP-PKA pathway has been shown to increase virus transcription (60). In HIV infection, undefined events involved in viral entry and infectivity are also under control of PKA (61,62). Finally, PKA-mediated phos- FIGURE 6.…”

The Nucleoside Triphosphate Diphosphohydrolase-1/CD39 Is Incorporated into Human Immunodeficiency Type 1 Particles, Where It Remains Biologically Active

“…19 The catalytic subunit of cAMP-dependent protein kinase Awas also shown to be packaged and to remain enzymatically active within mature HIV-1 particles. 20 This virus-associated protein kinase is thought to regulate virus infectivity by catalyzing phosphorylation of the viral capsid p24 protein. 20 Very few active ectoenzymes have been identified within the HIV-1 envelope.…”

“…20 This virus-associated protein kinase is thought to regulate virus infectivity by catalyzing phosphorylation of the viral capsid p24 protein. 20 Very few active ectoenzymes have been identified within the HIV-1 envelope. The complement control proteins CD55 and CD59 are incorporated into HIV-1 particles and have been shown to be active in complement breakdown.…”

“…These include actin cytoskeletal proteins, 13 cyclophilin A, 14,15 ubiquitin, 16 chromatin proteins, 17 as well as signaling molecules such as ERK2 mitogen-activated protein kinase, 18,19 and cAMPdependent protein kinase A. 20 Although the precise involvement of these cellular constituents in HIV-1 pathogenesis is still unclear, a number of host-encoded proteins have been shown to affect the viral life-cycle. For example, the adhesion molecule ICAM-1 and the costimulatory molecules CD28, CD80 and CD86 enhance HIV-1 infectivity by facilitating virus binding and entry into target cells that express their cognate ligands.…”

“…For example, the presence of an active catalytic subunit of cAMPdependent protein kinase Awithin HIV-1 is required for viral infectivity, possibly because of its ability to catalyze phosphorylation of the viral p24 capsid protein. 20 Hence, analyses aimed at assessing the function of host-encoded molecules that are found inserted within nascent viruses are needed to define whether this phenomenon might eventually affect disease progression.…”