Abstract
Macroautophagy (hereafter referred to as autophagy) is an intracellular degradative process, well conserved among eukaryotes. By engulfing cytoplasmic constituents into the autophagosome for degradation, this process is involved in the maintenance of cellular homeostasis. Autophagy induction triggers the formation of a cup-shaped double membrane structure, the phagophore, which progressively elongates and encloses materials to be removed. This double membrane vesicle, which is called an autophagosome, fuses with lysosome and forms the autolysosome. The inner membrane of the autophagosome, along with engulfed compounds, are degraded by lysosomal enzymes, which enables the recycling of carbohydrates, amino acids, nucleotides, and lipids. In response to various factors, autophagy can be induced for non-selective degradation of bulk cytoplasm. Autophagy is also able to selectively target cargoes and organelles such as mitochondria or peroxisome, functioning as a quality control system. The modification of autophagy flux is involved in developmental processes such as resistance to stress conditions, aging, cell death, and multiple pathologies. So, the use of animal models is essential for understanding these processes in the context of different cell types throughout the entire lifespan. For almost 15 years, the nematode Caenorhabditis elegans has emerged as a powerful model to analyze autophagy in physiological or pathological contexts. This review presents a rapid overview of physiological processes involving autophagy in Caenorhabditis elegans, the different assays used to monitor autophagy, their drawbacks, and specific tools for the analyses of selective autophagy.
Highlights
Macroautophagy is an intracellular degradative process, well conserved among eukaryotes
The co-localization approaches between LGG-1/LGG-2 and other proteins, for instance the autophagy substrate SEPA-1, are easy to perform by immunostaining in the embryo, but this approach is more complicated in larva or adult, especially for some tissues
The depletion of some autophagy proteins, such as BEC-1 and LGG-1, can be linked to sterility or lethality occurring during development, which can complicate their study at later stages
Summary
A Caenorhabditis elegans adult is an approximately 1 mm, transparent nematode, predominantly found as a self-fertilizing hermaphrodite. During the last 15 years, numerous studies on C. elegans have shown that autophagy is involved in multiple processes through embryonic and larval development. The degradation of several paternal organelles is dependent of the formation of autophagosomes This fast process, called allophagy (allogenic organelles autophagy), leads to the degradation of the sperm components by selective autophagy, and is linked to the polyubiquitination of these organelles [19,24]. Dying cells lead to the formation of cell corpses, and autophagy proteins (BEC-1, UNC-51, ATG-18) were shown to be involved in the removal of those corpses in germline cells. A first report demonstrated that the upregulation of autophagy has a role in limiting the growth of heterogeneous tumors in the gonad [41]
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