HIV-1 Nef Impairs the Formation of Calcium Membrane Territories Controlling the Signaling Nanoarchitecture at the Immunological Synapse

Abstract

The ability of HIV-1 to replicate and to establish long-term reservoirs is strongly influenced by T cell activation. Through the use of membrane-tethered, genetically encoded calcium (Ca2+) indicators, we were able to detect for the first time, to our knowledge, the formation of Ca2+ territories and determine their role in coordinating the functional signaling nanostructure of the synaptic membrane. Consequently, we report a previously unknown immune subversion mechanism involving HIV-1 exploitation, through its Nef accessory protein, of the interconnectivity among three evolutionarily conserved cellular processes: vesicle traffic, signaling compartmentalization, and the second messenger Ca2+. We found that HIV-1 Nef specifically associates with the traffic regulators MAL and Rab11b compelling the vesicular accumulation of Lck. Through its association with MAL and Rab11b, Nef co-opts Lck switchlike function driving the formation Ca2+ membrane territories, which, in turn, control the fusion of LAT-transporting Rab27 and Rab37 vesicles and the formation of LAT nanoclusters at the immunological synapse. Consequently, HIV-1 Nef disengages TCR triggering from the generation of p-LAT and p-SLP nanoclusters driving TCR signal amplification and diversification. Altogether our results indicate that HIV-1 exploits the interconnectivity among vesicle traffic, Ca2+ membrane territories, and signaling nanoclusters to modulate T cell signaling and function.