Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Nef enhances virus replication and contributes to immune evasion in vivo, but the underlying molecular mechanisms remain incompletely defined. Nef interferes with host cell actin dynamics to restrict T lymphocyte responses to chemokine stimulation...

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Autores principales:	Andrea Imle, Libin Abraham, Nikolaos Tsopoulidis, Bernard Hoflack, Kalle Saksela, Oliver T. Fackler
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/541c697a482f419082ce782f93454599
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spelling	oai:doaj.org-article:541c697a482f419082ce782f934545992021-11-15T15:41:31ZAssociation with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex10.1128/mBio.01309-152150-7511https://doaj.org/article/541c697a482f419082ce782f934545992015-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01309-15https://doaj.org/toc/2150-7511ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Nef enhances virus replication and contributes to immune evasion in vivo, but the underlying molecular mechanisms remain incompletely defined. Nef interferes with host cell actin dynamics to restrict T lymphocyte responses to chemokine stimulation and T cell receptor engagement. This relies on the assembly of a labile multiprotein complex including the host kinase PAK2 that Nef usurps to phosphorylate and inactivate the actin-severing factor cofilin. Components of the exocyst complex (EXOC), an octameric protein complex involved in vesicular transport and actin remodeling, were recently reported to interact with Nef via the same molecular surface that mediates PAK2 association. Exploring the functional relevance of EXOC in Nef-PAK2 complex assembly/function, we found Nef-EXOC interactions to be specifically mediated by the PAK2 interface of Nef, to occur in infected human T lymphocytes, and to be conserved among lentiviral Nef proteins. In turn, EXOC was dispensable for direct downstream effector functions of Nef-associated PAK2. Surprisingly, PAK2 was essential for Nef-EXOC association, which required a functional Rac1/Cdc42 binding site but not the catalytic activity of PAK2. EXOC was dispensable for Nef functions in vesicular transport but critical for inhibition of actin remodeling and proximal signaling upon T cell receptor engagement. Thus, Nef exploits PAK2 in a stepwise mechanism in which its kinase activity cooperates with an adaptor function for EXOC to inhibit host cell actin dynamics. IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) Nef contributes to AIDS pathogenesis, but the underlying molecular mechanisms remain incompletely understood. An important aspect of Nef function is to facilitate virus replication by disrupting T lymphocyte actin dynamics in response to stimulation via its association with the host cell kinase PAK2. We report here that the molecular surface of Nef for PAK2 association also mediates interaction of Nef with EXOC and establish that PAK2 provides an essential adaptor function for the subsequent formation of Nef-EXOC complexes. PAK2 and EXOC specifically cooperate in the inhibition of actin dynamics and proximal signaling induced by T cell receptor engagement by Nef. These results establish EXOC as a functionally relevant Nef interaction partner, emphasize the suitability of the PAK2 interaction surface for future therapeutic interference with Nef function, and show that such strategies need to target activity-independent PAK2 functions.Andrea ImleLibin AbrahamNikolaos TsopoulidisBernard HoflackKalle SakselaOliver T. FacklerAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 5 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Andrea Imle Libin Abraham Nikolaos Tsopoulidis Bernard Hoflack Kalle Saksela Oliver T. Fackler Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
description	ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Nef enhances virus replication and contributes to immune evasion in vivo, but the underlying molecular mechanisms remain incompletely defined. Nef interferes with host cell actin dynamics to restrict T lymphocyte responses to chemokine stimulation and T cell receptor engagement. This relies on the assembly of a labile multiprotein complex including the host kinase PAK2 that Nef usurps to phosphorylate and inactivate the actin-severing factor cofilin. Components of the exocyst complex (EXOC), an octameric protein complex involved in vesicular transport and actin remodeling, were recently reported to interact with Nef via the same molecular surface that mediates PAK2 association. Exploring the functional relevance of EXOC in Nef-PAK2 complex assembly/function, we found Nef-EXOC interactions to be specifically mediated by the PAK2 interface of Nef, to occur in infected human T lymphocytes, and to be conserved among lentiviral Nef proteins. In turn, EXOC was dispensable for direct downstream effector functions of Nef-associated PAK2. Surprisingly, PAK2 was essential for Nef-EXOC association, which required a functional Rac1/Cdc42 binding site but not the catalytic activity of PAK2. EXOC was dispensable for Nef functions in vesicular transport but critical for inhibition of actin remodeling and proximal signaling upon T cell receptor engagement. Thus, Nef exploits PAK2 in a stepwise mechanism in which its kinase activity cooperates with an adaptor function for EXOC to inhibit host cell actin dynamics. IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) Nef contributes to AIDS pathogenesis, but the underlying molecular mechanisms remain incompletely understood. An important aspect of Nef function is to facilitate virus replication by disrupting T lymphocyte actin dynamics in response to stimulation via its association with the host cell kinase PAK2. We report here that the molecular surface of Nef for PAK2 association also mediates interaction of Nef with EXOC and establish that PAK2 provides an essential adaptor function for the subsequent formation of Nef-EXOC complexes. PAK2 and EXOC specifically cooperate in the inhibition of actin dynamics and proximal signaling induced by T cell receptor engagement by Nef. These results establish EXOC as a functionally relevant Nef interaction partner, emphasize the suitability of the PAK2 interaction surface for future therapeutic interference with Nef function, and show that such strategies need to target activity-independent PAK2 functions.
format	article
author	Andrea Imle Libin Abraham Nikolaos Tsopoulidis Bernard Hoflack Kalle Saksela Oliver T. Fackler
author_facet	Andrea Imle Libin Abraham Nikolaos Tsopoulidis Bernard Hoflack Kalle Saksela Oliver T. Fackler
author_sort	Andrea Imle
title	Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
title_short	Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
title_full	Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
title_fullStr	Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
title_full_unstemmed	Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex
title_sort	association with pak2 enables functional interactions of lentiviral nef proteins with the exocyst complex
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/541c697a482f419082ce782f93454599
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Association with PAK2 Enables Functional Interactions of Lentiviral Nef Proteins with the Exocyst Complex

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