Arf GTPases Define BST-2-Independent Pathways for HIV-1 Assembly and Release.

UNLABELLED

ADP-ribosylation factor (Arf) proteins are small GTPases that regulate intracellular membrane trafficking and actin cytoskeleton remodeling through cycles of GTP binding and hydrolysis. Arf1, a central regulator of Golgi and endosomal trafficking, and Arf6, which controls plasma membranes and endosomal dynamics, have both been implicated in late stages of the HIV-1 life cycle. However, the precise mechanisms by which these GTPases support HIV-1 assembly and release remain incompletely understood. Here, we provide direct evidence that Arf1 and Arf6 are required for efficient trafficking of the HIV-1 Gag polyprotein, assembly, and virion release. Perturbation of Arf1 function with either a GTP-locked (Q71L) or GDP-locked (T31N) mutant significantly reduced virus release, impaired Gag association with membrane compartments, and blocked Gag targeting to the plasma membrane. Manipulation of Arf1 activity via the GTPase-activating protein AGAP1 further demonstrated that dynamic cycling of Arf1 between GTP- and GDP-bound states is essential for productive Gag trafficking. Similarly, expression of a constitutively active Arf6 mutant (Q67L) misdirected Gag to intracellular membranes and markedly decreased virion production. Importantly, disruption of Arf1 or Arf6 function did not affect the total expression, surface levels, or intracellular distribution of the host restriction factor BST-2. Together, these findings establish that Arf1- and Arf6-mediated trafficking pathways are critical host determinants of HIV-1 assembly and release, functioning independently of BST-2 antagonism.

IMPORTANCE

The small GTPases Arf1 and Arf6 control fundamental processes in membrane trafficking and cytoskeletal dynamics, yet their roles in HIV-1 replication are not well defined. We show that both proteins are required for efficient trafficking of HIV-1 Gag polyprotein to the plasma membrane and for subsequent virus release. Disrupting either GTPase reroutes Gag to intracellular membranes and reduces virion production, independently of the antiviral host factor BST-2. These results identify Arf1- and Arf6-dependent trafficking as critical host pathways for HIV-1 assembly and egress, expanding our understanding of the cellular machinery hijacked by retroviruses to support infections.