LC3-associated phagocytosis (LAP) is a process wherein elements of canonical autophagy conjugate LC3 to the membranes of phagosomes, facilitating maturation upon fusion to lysosomes. Here, we characterize the molecular requirements for LAP, and identify a protein, Rubicon, required for LAP but not canonical autophagy. During LAP, Rubicon is recruited to the LAP-engaged phagosome (“LAPosome”) and is required for the activity of a Class III PI3K complex containing Beclin-1, UVRAG, and VPS34, but lacking the canonical autophagy components ATG14 and Ambra1. This allows for the sustained localization of PI(3)P, which is critical for the recruitment of downstream autophagic proteins and the stabilization of the NOX2 complex to produce ROS. Both PI(3)P and ROS, as well as ATG7, ATG3, ATG5, ATG12, and ATG16L, are required for the conjugation of LC3 to the LAPosome and subsequent association with LAMP1+ lysosomes. LAP is also induced by engulfment of Aspergillus fumigatus, a fungal pathogen that commonly afflicts immunocompromised hosts, and is required for its optimal clearance in vivo. Therefore, we have identified molecules that distinguish LAP from canonical autophagy, thereby elucidating the importance of LAP in the response to Aspergillus fumigatus infection.

Genetic variation in CHRNA5, the gene encoding the α5 nicotinic acetylcholine receptor (nAChR) subunit, increases vulnerability to tobacco addiction and lung cancer, but underlying mechanisms are unknown. Here, we report dramatically increased nicotine consumption in mice with null mutation in Chrna5. This effect was `rescued' in knockout mice by re-expressing α5 subunits in medial habenula (MHb), and recapitulated in rats through α5 subunit knockdown in MHb. Remarkably, α5 subunit knockdown in MHb did not alter the rewarding effects of nicotine but abolished the inhibitory effects of higher nicotine doses on brain reward systems. The MHb extends projections almost exclusively to the interpeduncular nucleus (IPN). We found diminished IPN activation in response to nicotine in α5 knockout mice and disruption of IPN signaling increased nicotine intake in rats. Our findings suggest that nicotine activates the habenulo-interpeduncular pathway through α5-containing nAChRs, triggering an inhibitory motivational signal that acts to limit nicotine intake.

The molecular understanding of autophagy has originated almost exclusively from yeast genetic studies. Little is known about essential autophagy components specific to higher eukaryotes. Here we perform genetic screens in C. elegans and identify four metazoan-specific autophagy genes, named epg-2, -3, -4, and -5. Genetic analysis reveals that epg-2, -3, -4, and -5 define discrete genetic steps of the autophagy pathway. epg-2 encodes a coiled-coil protein that functions in specific autophagic cargo recognition. Mammalian homologs of EPG-3/VMP1, EPG-4/EI24, and EPG-5/mEPG5 are essential for starvation-induced autophagy. VMP1 regulates autophagosome formation by controlling the duration of omegasomes. EI24 and mEPG5 are required for formation of degradative autolysosomes. This study establishes C. elegans as a multicellular genetic model to delineate the autophagy pathway and provides mechanistic insights into the metazoan-specific autophagic process.

Cocaine addiction is characterized by a gradual loss of control over drug use, but molecular mechanisms regulating vulnerability to this process remain unclear. Here we report that microRNA-212 (miR-212) is upregulated in the dorsal striatum of rats with a history of extended access to cocaine. Striatal miR-212 decreases responsiveness to the motivational properties of cocaine by dramatically amplifying the stimulatory effects of the drug on CREB signaling. This action occurs through miR-212-enhanced Raf-1 activity, resulting in adenylyl cyclase sensitization and increased expression of the essential CREB co-activator TORC (Transducer of Regulated CREB; also known as CRTC). Our findings suggest that striatal miR-212 signaling plays a key role in determining vulnerability to cocaine addiction, reveal novel molecular regulators that control the complex actions of cocaine in brain reward circuitries, and provide an entirely new direction for the development of anti-addiction therapeutics based on modulation of noncoding RNAs.

Defects in dying cell clearance are postulated to underlie the pathogenesis of systemic lupus erythematosus (SLE)1. Mice lacking molecules associated with dying cell clearance develop SLE-like disease2, and phagocytes from SLE patients often display defective clearance and increased inflammatory cytokine production when exposed to dying cells in vitro. Previously, we3–6 and others7 described a form of noncanonical autophagy called “LC3-associated phagocytosis” (LAP), wherein phagosomes containing engulfed particles, including dying cells3,4,7, recruit elements of the autophagy pathway to facilitate phagosome maturation and digestion of cargo. Genome-wide association studies have identified polymorphisms in atg58 and possibly atg79, involved in both canonical autophagy and LAP3–7, as predisposition markers for SLE. Here, we describe the consequences of defective LAP in vivo. Mice lacking any of several components of the LAP pathway display elevated serum inflammatory cytokines, autoantibodies, glomerular immune complex deposition, and evidence of kidney damage. Dying cells, injected into LAP-deficient animals, are engulfed but not efficiently degraded, and trigger acute elevation of pro-inflammatory cytokines but not the anti-inflammatory interleukin (IL)-10. Repeated injection of dying cells into LAP-deficient, but not LAP-sufficient animals accelerated SLE-like disease, including increased serum levels of autoantibodies. In contrast, animals deficient for genes required for canonical autophagy but not LAP do not display defective dead cell clearance, inflammatory cytokine production, or SLE-like disease, and like wild-type animals, produce IL-10 in response to dying cells. Therefore, defects in LAP, rather than canonical autophagy, can cause SLE-like phenomena, and may contribute to the pathogenesis of SLE.