Phagocytosis of Candida albicans Inhibits Autophagic Flux in Macrophages

Abstract

Autophagy machinery has roles in the defense against microorganisms such as Candida albicans. Lipidated LC3, the marker protein of autophagy, participates in the elimination of C. albicans by forming a single-membrane phagosome; this process is called LC3-associated phagocytosis (LAP). However, the influence of C. albicans on autophagic flux is not clear. In this study, we found that C. albicans inhibited LC3 turnover in macrophages. After the phagocytosis of C. albicans in macrophages, we observed fewer acridine orange-positive vacuoles and RFP-GFP-LC3 puncta without colocalization with phagocytized C. albicans. However, phagocytosis of C. albicans led to LC3 recruitment, but p62 and ATG9A did not colocalize with LC3 or C. albicans. These effects are due to an MTOR-independent pathway. Nevertheless, we found that the C. albicans pattern-associated molecular pattern β-glucan increased LC3 turnover. In addition, phagocytosis of C. albicans caused a decrease in BrdU incorporation. Blocking autophagic flux aggravated this effect. Our findings suggest that phagocytosis of C. albicans decreases autophagic flux but induces LAP in an MTOR-independent manner in macrophages. Occupation of LC3 by recruiting engulfed C. albicans might contribute to the inhibition of autophagic flux. Our study highlights the coordinated machinery between canonical autophagy and LAP that defends against C. albicans challenge.

Granulosa cells provide elimination of apoptotic oocytes through unconventional autophagy-assisted phagocytosis

“…In contrast to classical phagocytosis cups, those formed during LAP contain several autophagy proteins (Kim et al, 2013;Panneerdoss et al, 2017;Duan et al, 2018). Thus, Beclin1 and ATG5 proteins are known to be recruited to phagosomal membranes as a very early event in LAP (Martinez et al, 2011;Kim et al, 2013;Li et al, 2013).…”

“…In our KGN cell model, we observed an increase of the expression of ATG5 protein during phagocytosis of apoptotic oocytes, while those of ATG7 did not vary. The formation of phagocytic cups and the ingestion of apoptotic substrates progress through activation of a downstream effector, Ras-related C3 botulinum toxin substrate (RAC1), which mediates actin reorganization (Kim et al, 2013;Teplova et al, 2013;Panneerdoss et al, 2017;Duan et al, 2018). While the order of events in the signaling pathways remains an A c c e p t e d m a n u s c r i p t unaddressed question (Heckmann et al, 2017), the recruitment of autophagy proteins seems to be necessary to sustain MERTK-mediated ingestion.…”

GINS2 affects cell proliferation, apoptosis, migration and invasion in thyroid cancer via regulating MAPK signaling pathway

“…Furthermore, cell apoptosis was increased in K1 and SW579 cells following GINS2 silencing by in situ fluorescence detection. Previous studies have demonstrated that in situ fluorescence assay can verify the change of apoptosis rate ( 38 , 39 ). Alternatively, caspase-3 activity and other techniques can also be applied for cell apoptosis assay, which will be performed in further studies.…”

La phagocytose associée à LC3 (LAP)

“…La LAP joue un rôle essentiel au cours des infections fongiques. Elle a été décrite notamment dans le cas d'infections par les champignons Aspergillus [24], Candida albicans [25], Saccharomyces cerevisiae [5] ou Rhizopus spp [26]. Ainsi, suite à leur phagocytose, les conidies d'Aspergillus fumigatus, spores assurant la multiplication du champignon, gonflent, exposant alors en surface des β-glucanes, sucres habituellement masqués par sa paroi, qui sont reconnus et activent la cellule [24] par la voie Dectine-1-Syk-NOX2.…”