Human T Cell Leukemia Virus Envelope Binding and Virus Entry Are Mediated by Distinct Domains of the Glucose Transporter GLUT1

Abstract

The glucose transporter GLUT1, a member of the multimembrane-spanning facilitative nutrient transporter family, serves as a receptor for human T cell leukemia virus (HTLV) infection. Here, we show that the 7 amino acids of the extracellular loop 6 of GLUT1 (ECL6) placed in the context of the related GLUT3 transporter were sufficient for HTLV envelope binding. Glutamate residue 426 in ECL6 was identified as critical for binding. However, binding to ECL6 was not sufficient for HTLV envelope-driven infection. Infection required two additional determinants located in ECL1 and ECL5, which otherwise did not influence HTLV envelope binding. Moreover the single N-glycosylation chain located in ECL1 was not required for HTLV infection. Therefore, binding involves a discrete determinant in the carboxyl terminal ECL6, whereas post-binding events engage extracellular sequences in the amino and carboxyl terminus of GLUT1.Interactions of retroviral envelope glycoproteins (Env) 1 with cell surface receptors govern the first steps of retroviral infection. Env mediates both virus binding to the cell surface and fusion of the viral and cellular membranes allowing productive viral entry. Env consists of an extracellular surface component (SU) and an associated transmembrane subunit (TM) harboring an amino-terminal fusion peptide (1). SU and TM are derived from the same polyprotein precursor (1), and it is generally accepted that initial interactions between SU and the receptor are sufficient to induce post-binding conformational changes of Env that unmask the TM fusion peptide (2).Several Env determinants of gammaretroviruses distinctively involved in binding and post-binding events have been described (3)(4)(5)(6)(7)(8). From the context of the cellular Env receptors, little is known concerning potential post-binding determinants and receptor conformational changes that follow SU binding (9, 10). In the case of HIV and other related lentiviruses, it has been shown that post-binding events involve the recruitment of additional molecules, co-receptors, that belong to the seven membrane-spanning chemokine receptor family (11). No such co-receptors have yet been reported for a non-lentiviral Env (12). Human T cell leukemia virus (HTLV) is a complex deltaretrovirus characterized by several multispliced mRNAs that encode for regulatory proteins. However, despite the large phylogenetic distance (13) between HTLV and simple gammaretroviruses, HTLV and murine leukemia viruses (MLVs) share a common general organization of Env (14 -16). Their respective SU are composed of an amino-terminal RBD (14 -18) followed by a central proline-rich region (15, 19) and a carboxyl-terminal domain that harbors a conserved (20) and highly reactive CXXC motif (6,8). Furthermore, the HTLV Env receptor, the glucose transporter 1 (GLUT1) (21), is a multimembrane-spanning molecule, like all identified gammaretrovirus receptors (22).In this context, we sought to identify GLUT1 determinants that are involved in the different steps of HTLV Env-mediated viral ent...

Transmission intercellulaire de HTLV-1

“…GLUT-1, un transporteur du glucose fortement exprimé par les cellules T activées, est ensuite impliqué dans l'entrée du virus. Le niveau d'expression de GLUT-1 à la surface des cellules n'est cependant pas corrélé au niveau de fixation de la protéine virale d'enveloppe SU [10], suggérant que GLUT-1 intervient dans les évène-ments tardifs de l'entrée (étape de fusion) [11]. Une troisième molécule contribue à l'entrée du virus.…”

How Does Susceptibility to HTLV-1 Infection Varies With the Maturation State of Dendritic Cells?

“…This shows that the pH of the compartments in which HTLV-1 is stored after capture determines the efficiency of productive infection. This could be due to instability of HTLV-1 envelope under acidic conditions, thus impairing the subsequent Glut-1-dependent fusion with the cellular membrane and viral capsid release in the cell cytoplasm [23]. This would explain the absence of proviral DNA detection in mature DCs [10].…”

“…Of note, CD82 is known to localize at the plasma membrane and to interact with HTLV-1 envelope SU glycoprotein in T cells [22]. Thus, in addition to its interaction with HTLV-1 receptor complex containing Glut-1 [23], HTLV-1 Env interaction with CD82 could direct HTLV-1 to unconventional compartments. However, because HTLV-1 localization is similar in immature and mature DCs, targeting of incoming particles to specific compartments cannot explain viral restriction in mature DCs.…”

Optimization of tumor xenograft dissociation for the profiling of cell surface markers and nutrient transporters

“…5,6 Here, cell surface expression of four metabolite transporters was monitored using retroviral RBDs that bind to the exofacial determinants of Glut1, ASCT2, PiT1 and PiT2. These transporters are cognate receptors for HTLV, 11,28 feline RD114 endogenous retrovirus, 29 KoRV 30 and amphotropic murine leukemia virus 7,8,30,31 Env, respectively. We assessed cell surface expression of these transporters in five human breast cancer models with different molecular characteristics (Supplementary Table 1) and found that the transporter expression profile of each tumor was unique ( Figure 6).…”