THE HIV-1 ACCESSORY PROTEIN VPU TARGETS HOST SLC1A5 (ASCT2) AMINO ACID TRANSPORTER

LUCIANA MORELLATTO RUGGIERI; JAVIER G. MAGADAN; AYMÉ DRAKE

Encuentro; LVI Reunión Anual de la SAIB y XV Reunión Anual de la SAMIGE; 2020

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

In order to infect a new host, replicate on it for many years, and spread to new individuals, the Human Immunodeficiency Virus 1 (HIV-1) should avoid not only their innate defenses, including antiviral restriction factors, but also humoral and cellular adaptive responses. To date, many restriction factors that actively act against HIV-1 have been identified, including APOBEC3G, TRIM5α, cyclophilin A, BST-2/tetherin, SAMHD1, and SERINC3/5. HIV-1 has evolved a variety of mechanisms to evade these factors by either acquiring mutations in the viral proteins susceptible to their action or encoding specific "accessory" proteins that eventually neutralize them. Thus, Vpu and Nef, among the most well-known viral accessory factors, act as molecular adapters that connect specific cellular targets with proteolytic or alternative intracellular trafficking pathways. By setting-up a tandem purification approach, we obtained a complete proteomic profile of the host proteins that specifically interact with HIV-1 Vpu. Among them, we have put SLC1A5 (ASCT2) into the test by further analyzing its role in HIV-1 pathogenesis. ASCT2 is a neutral amino acid transporter coupled to Na+ gradient, which is also relevant for human health due to its involvement in the homeostasis, activation, differentiation of naive T cells, especially Th1, Th17, and memory T cells, and its function as a receptor of several retroviruses, such as mammalian type D and BaEV and RD114 type C. Our results indicate that Vpu-ASCT2 interaction depends on the Vpu transmembrane domain and it is not affected by mutating a Vpu cytosolic domain comprising both phospho-serines 52 and 56, a structural motif recognized by the host E3 ubiquitin ligase SCF. In addition, over-expression of viral Vpu in HeLa cells promotes the redistribution of ASCT2, causing a depletion of this amino acid transporter levels in HeLa cells. Altogether, these data suggest that ASCT2 is a putative host cell factor targeted by Vpu, whose function might be critically important during the infectious cycle of HIV-1