LAPTM5 Downregulation-Driven VAMP8 Phosphorylation Impairs Autophagosome-Lysosome Fusion and Aggravates Septic Acute Lung Injury.

Summary

Using septic acute lung injury patient samples, mouse models, and macrophage-specific manipulation, the study identified LAPTM5 as a key regulator of macrophage autophagic homeostasis. LAPTM5 links PGAM5 to VAMP8, promotes PGAM5-dependent VAMP8 dephosphorylation and autophagosome–lysosome fusion, thereby clearing damaged mitochondria and reducing oxidative stress and inflammation.

Key Findings

• LAPTM5 was markedly downregulated in peripheral blood mononuclear cells from septic acute lung injury patients and in alveolar macrophages from septic mice, with inverse correlation to SOFA score.
• Macrophage-specific Laptm5 depletion worsened, whereas AAV-mediated Laptm5 overexpression improved, septic acute lung injury in mice.
• LAPTM5 scaffolding of PGAM5 and VAMP8 promoted VAMP8 dephosphorylation, autophagosome–lysosome fusion, mitochondrial clearance, and suppression of oxidative stress and inflammation.

Clinical Implications

LAPTM5 expression or the associated autophagy pathway could eventually support risk stratification or targeted therapy for septic acute lung injury. Translation is currently preclinical; no change to standard sepsis or acute lung injury treatment is justified yet.

Limitations

• The therapeutic findings remain confined to preclinical models and have not established safety, pharmacokinetics, or efficacy in humans.
• The abstract does not establish whether LAPTM5 changes are a cause of disease severity or partly a consequence of systemic inflammation.

Future Directions

Future work should develop pharmacologic or genetic strategies to enhance LAPTM5 activity, validate the pathway in independent human cohorts, and determine whether LAPTM5-based interventions improve survival without impairing antimicrobial host defense.