Turcotte, E. | bioRxiv Science

bioRxiv2022

A human-specific motif facilitates CARD8 inflammasome activation after HIV-1 infection

Inflammasomes are cytosolic innate immune complexes that play a critical role in host defense against pathogens but can also contribute to inflammatory pathogenesis. Here, we find that the human inflammasome-forming sensor CARD8 senses HIV-1 infection via site-specific cleavage of the CARD8 N-terminus by the HIV protease (HIV-1PR). HIV-1PR cleavage of CARD8 induces pyroptotic cell death and the release of pro-inflammatory cytokines from infected cells, processes that we find are dependent on Toll-like receptor stimulation prior to viral infection. Our evolutionary analyses reveal that the HIV-1PR cleavage site in CARD8 is unique to humans, and that chimpanzee CARD8 does not recognize proteases from HIV or simian immunodeficiency viruses from chimpanzees (SIVcpz). In contrast, SIVcpz does cleave human CARD8, suggesting that SIVcpz was poised to activate the human CARD8 inflammasome prior to its cross-species transmission into humans and implicating the CARD8 inflammasome as a potential driver of HIV pathogenesis.

microbiology↗

bioRxiv2020

The Nuclear Pore Complex consists of two independent scaffolds

Macromolecular transport between the nucleus and cytoplasm is mediated through Nuclear Pore Complexes (NPCs), which are built from multiple copies of roughly 34 distinct proteins, called nucleoporins1-3. Models of the NPC depict it as a composite of several sub-domains that have been named the outer rings, inner ring, cytoplasmic fibrils and nuclear basket. While the NPC has been extensively studied, the roles of individual nucleoporins within NPCs and their functional interactions remain poorly understood. Here, we applied a rapid degron system to systematically investigate how individual nucleoporins contribute toward NPC architecture. We find that acute depletion of outer ring components (NUP96 or NUP107) disperses the outer ring and cytoplasmic fibrils without disassembly of inner ring members. Conversely, rapid degradation of the inner ring complex component NUP188 disrupts the inner ring without dislodging outer ring members. We also found that depletion of NUP93 destabilized all NPC domains, indicating that it has a unique role as a lynchpin of NPC structure. Our data highlight the modular nature of NPC organization, suggesting that the outer and inner ring complexes do not extensively rely on each other for structural stability after NPC assembly is complete. This dynamic assessment provides new insights regarding the remarkable structural independence of domains within the NPC.

cell biology↗