Does Autophagy Play a Role in Disease?

Autophagy is highly conserved process wherein parts of eukaryotic cells are self-digested within a lysosome or vacuole and the cellular contents are degraded and recycled. Derived from the Greek word meaning to eat (“phagy”) oneself (“auto”), the term autophagy refers to a lysosomal degradation pathway of self-digestion. The molecular machinery of autophagy was first discovered in budding yeast Saccharomyces cerevisae as a model system, operating in all eukaryotic organisms but not in that of any prokaryotes. Autophagic activity is critical to the maintenance of cellular homeostasis and energy balance. Although typically low under basal conditions, autophagy can be markedly upregulated by a variety of physiological stimuli such as nutrient starvation, hypoxia, endoplasmic reticulum stress, as well as immune and hormonal stimulation. Mounting evidence has connected malfunctions in autophagic processes to many clinically relevant diseases including cancer, neurodegeneration, diabetes, autoimmunity, and cardiovascular disease. Development of autophagy-targeting therapies will depend on a deeper understanding of the benefits, and potential consequences, of altering autophagic activity. Enzo Life Sciences offers a broad portfolio of research tools for your Autophagy research needs.

Different subtypes of autophagy have been distinguished by the cargo that is being degraded. The most extensively studied form of autophagy, macroautophagy, degrades large portions of the cytoplasm and cellular organelles. Non-selective autophagy occurs continuously, and is efficiently induced in response to stress, e.g. starvation. Additionally, the selective autophagy of specific classes of substrates - protein aggregates, cytoplasmic organelles or invading viruses and bacteria, involves specific adaptors that recognize the cargo and targets it on the autophagosomal membrane. Other forms of autophagy include microautophagy, which involves the direct engulfment of cytoplasmic material via inward folding of the lysosomal membrane, and chaperone-mediated autophagy (CMA). In CMA, proteins with specific recognition signals are directly translocated into the lysosome via binding to a chaperone complex.

Originally characterized as a hormonal and starvation response, autophagy has a much broader role in biology, including organelle remodeling, protein and organelle quality control, prevention of genotoxic stress, tumor suppression, pathogen elimination, regulation of immunity and inflammation, maternal DNA inheritance, metabolism, and cellular survival. Although autophagy is a degradative pathway, it also participates in biosynthetic and secretory processes. Given that autophagy has a fundamental role in many essential cellular functions, it is not surprising that autophagic dysfunction is associated with a wide range of human diseases. Misfolded proteins tend to form insoluble aggregates that are toxic to cells. Enzo’s PROTEOSTAT® Protein Aggregation Assay can quantitatively detection protein aggregates from visible to sub-visible particles. To cope with this problem, cells depends on autophagy. The field has become one of the most intensely studied areas of biomedical research, with a remarkable increase in the number of publications since the early 2000’s. Furthermore, the Nobel Committee recognized the breakthrough by the awarding of the 2016 Nobel Prize in Physiology or Medicine for research in autophagy.

What makes autophagy unique? The answer lies in the flexibility of autophagosome size and cargo selection. Autophagy can promote degradation en masse for a large number and variety of substrates, enabling cells to quickly and efficiently generate recycled basic building materials in the face of a wide range of nutritional deficiencies. Additionally, autophagy is the only pathway that is capable of degrading entire organelles, either randomly or in a targeted fashion—a critical process for maintaining homeostasis in the complex landscape of the eukaryotic cell. This process ensures a quality control mechanism that is critical for counteracting the negative consequences of aging. Disrupted autophagy has been linked to Parkinson's disease, type 2 diabetes and other disorders that occur in the elderly. Mutations in cell death autophagy genes can cause genetic disease. Disturbances in the autophagic machinery have also been linked to cancer. Levels of autophagy have been observed to be elevated in cancer cells since the tumor microenvironment is hypoxic. Further research is now ongoing to develop drugs that can target autophagy in various diseases.

Autophagy is a dynamic, multistep process including autophagosome formation, autolysosome formation, and degradation of autophagic substrate, often denoted as autophagic flux. The formation of autophagosomes, a bilayer membrane vesicle which engulfs cytosolic components into lysosomes for degradation and recycling, is the indicator of autophagy. During autophagy activation, the cytoplasmic form microtubule-associated protein 1 light chain LC3 (LC3 I) is lipidated and recruited to the autophagosomes. LC3 II, which is the lipidated form of LC3, is attached to the autophagosome membrane, making LC3 conversion a prerequisite for autophagosome formation. The commonly used assay for monitoring autophagic flux is the turnover of LC3B or SQSTM1/p62 using immunoblotting, which measures the content through autophagic flux. However, this approach is time-consuming and labor intensive and the results are often varied in different experimental settings and hard to interpret. Realizing the need for a robust method to label autophagic compartments with minimal staining of lysosomes and endosomes, scientists at Enzo developed our CYTO-ID® fluorescence dye, which is a novel approach for detecting autophagy. Our CYTO-ID® Autophagy Detection Kit is a no-transfection, quantitative assay for monitoring autophagy and estimating autophagic flux in live cells. Additionally, we offer our SCREEN-WELL® Autophagy Library, which contains 94 compounds with defined autophagy-inducing or -inhibitory activity. This is a useful tool for studying the roles of pro- and anti-autophagic molecules in cells as well as for use in in vitro applications

The recent progress in identifying genes required for selective autophagy, many of which are mutated in human diseases, particularly cancer, and neurodegenerative disorders, holds great promise for the development of therapeutic treatments. Enzo Life Sciences offers a range of products for your Cellular Analysis research needs. As Scientists Enabling Healthcare, Enzo supports scientists in gaining a deeper understanding of the benefits, and potential consequences, of altering autophagic activity. Please check out our Tools for Studying Cell Death and Monitoring Autophagy in Live Cells Without Transfection or contact our Technical Support Team for further assistance.

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