Optineurin Deficiency Collapses the Host Endolysosomal Network and Impairs Xenophagy to Accelerate Mycobacterium tuberculosis Growth
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Selective autophagy is a host defense mechanism against Mycobacterium tuberculosis ( Mtb ) that restricts bacterial growth by targeting ubiquitin-coated bacilli for lysosomal degradation via autophagy receptors. Optineurin is a selective autophagy receptor that targets pathogens and modulates immune signaling; however, its precise structural mechanism during Mtb infection remains poorly defined. Here, we show that while Optineurin deficiency spares the global host transcriptomic response to infection, it collapses the host endolysosomal network, reducing LAMP1⁺ and LysoTracker⁺ reserves by half and 30%, respectively. Multi-dose bafilomycin A1 flux assays demonstrated that this structural depletion selectively blocks the dynamic, directional trafficking and functional delivery of autophagosomes to the pathogen, significantly reducing Mtb -DQ-BSA colocalization. Genetic complementation restored bacterial restriction in a manner dependent on three phosphosites (Ser187, Ser530, and the uncharacterized Ser556). In the context of reduced autophagic containment and increased Mtb replication, Optineurin deficiency accelerated necrotic-like host cell death. In vivo , Optineurin deficiency enhanced bacterial replication and impaired the Type I interferon response during acute Mtb infection but did not affect long-term survival. Together, these findings identify Optineurin as a critical regulator of autophagic flux, host cell death, and Type I interferon responses that limit early Mtb pathogenesis.
Importance
Tuberculosis remains a major global health threat in part because Mycobacterium tuberculosis can survive and replicate inside immune cells meant to destroy it. Host cells use a specialized cellular recycling and defense system, called autophagy, to capture and eliminate these intracellular bacteria. In this study, we identified a critical cellular protein, Optineurin, that serves as an essential sensor initiating this defense mechanism during infection. We discovered that chemical modifications, specifically phosphorylation, act as molecular switches that activate Optineurin’s protective functions. Without this protein, host cells control bacterial growth less effectively, suffer premature cell death, and partially lose their ability to mount early cytokine responses. By uncovering how Optineurin coordinates these diverse defense pathways, our findings provide a deeper understanding of early host-pathogen interactions and reveal potential molecular targets for developing novel, host-directed therapies to combat tuberculosis.
