Project description:LC3-associated phagocytosis (LAP) represents a non-canonical function of autophagy proteins in which ATG8 family proteins (LC3 and GABARAP proteins) are lipidated onto single-membrane phagosomes as particles are engulfed by phagocytic cells. LAP plays roles in innate immunity, inflammation and anti-cancer responses and is initiated upon phagocytosis of particles that stimulate Toll-like receptors (TLR), Fc-receptors, and upon engulfment of dying cells. However, how this molecular process is initiated remains elusive. Here we report that receptors that engage LAP enrich phosphatidylserine (PS) in the phagosome membrane via membrane-proximal domains that are necessary and sufficient for LAP to proceed. Subsequently, PS recruits the Rubicon-containing PI3-kinase complex to initiate the enzymatic cascade leading to LAP. Manipulation of plasma membrane PS content, PS-binding by Rubicon, or the PS-clustering domains of receptors prevents LAP and phagosome maturation. Therefore, the initiation of LAP represents a novel mechanism of PS-mediated signal transduction upon ligation of surface receptors.
Project description:Although innate immunity is critical for antifungal host defense against the human opportunistic fungal pathogen Aspergillus fumigatus, potentially damaging inflammation must be controlled. Adiponectin (APN) is an anti-inflammatory adipokine, and we observed 100% mortality and increased fungal burden and inflammation in neutropenic mice with invasive aspergillosis (IA) that lack APN or the APN receptors AdipoR1 or AdipoR2. Alveolar macrophages (AMs), early immune sentinels that detect and respond to lung infection, express both receptors, and APN-/- AMs exhibited an inflammatory/M1 phenotype that was associated with decreased fungal killing and decreased activation of LC3-associated phagocytosis (LAP). Furthermore, AM treatment with the AdipoR agonist AdipoRon partially rescued deficient killing in APN-/- AMs that was dependent on both receptors. Our study identifies a novel role for APN in LC3-mediated killing of A.fumigatus.
Project description:Mycobacterium tuberculosis impairs host lysosomal trafficking pathways. Xenophagy and LC3-associated phagocytosis (LAP) are lysosomal trafficking pathways that normally clear intracellular microbes. The xenophagy and LAP pathways depend upon ATG5 and ATG7, which result in the lipidation of LC3-I to LC3-II. How Mtb undermines these innate immune defenses of the host in not well understood. We used a transposon sequencing (Tn-seq) screen to identify bacterial factors that are required for the bacilli to resist ATG5 and ATG7-dependent processes. We found that that mutants defective in production of PDIM are attenuated in murine macrophages, and they are able to survive in macrophages lacking ATG5 or ATG7.
Project description:Phagocytic clearance of apoptotic germ cells by Sertoli cells is vital for germ cell development and differentiation. Using a tissue-specific miRNA transgenic mouse model, we show that interaction between miR-471-5p and autophagy member proteins regulates clearance of apoptotic germ cells via LC3-associated phagocytosis (LAP).
