Intrinsic properties and plasma membrane trafficking route of Src family kinase SH4 domains sensitive to retargeting by HIV-1 Nef [Microbiology]

March 27th, 2018 by Amanda J. Chase, Rebecka Wombacher, Oliver T. Fackler

The HIV-1 pathogenicity factor Nef enhances viral replication by modulating multiple host cell pathways, including tuning the activation state of infected CD4 T lymphocytes to optimize virus spread. For this, Nef inhibits anterograde transport of the Src family kinase (SFK) Lck toward the plasma membrane (PM). This leads to retargeting of the kinase to the trans-Golgi network (TGN), while the intracellular transport of a related SFK, Fyn, is unaffected by Nef. The 18 amino acid SH4 domain membrane anchor of Lck is necessary and sufficient for Nef-mediated retargeting, but other details of this process are not known. The goal of this study was therefore to identify characteristics of SH4 domains responsive to Nef and the transport machinery used. Screening a panel of SFK SH4 domains revealed two groups that were sensitive or insensitive for TGN retargeting by Nef, as well as the importance of the amino acid at position 8 for determining Nef-sensitivity. Anterograde transport of Nef-sensitive domains was characterized by slower delivery to the PM and initial targeting to Golgi membranes, where transport was arrested in the presence of Nef. For Nef-sensitive SH4 domains, ectopic expression of the lipoprotein binding chaperone (LPC) Unc119a or the GTPase Arl3 or reduction of their endogenous expression phenocopied the effect of Nef. Together, these results suggest that (i) analogous to K-Ras, Nef-sensitive SH4 domains are transported to the PM by a cycle of solubilization and membrane insertion and (ii) intrinsic properties define SH4 domains as cargo of this Nef-sensitive LPC-GTPase transport cycle.
  • Posted in Journal of Biological Chemistry, Publications
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