Akiko Kuma

Bio: Akiko Kuma is an academic researcher from Osaka University. The author has contributed to research in topics: Autophagy & ATG5. The author has an hindex of 18, co-authored 28 publications receiving 5943 citations. Previous affiliations of Akiko Kuma include Graduate University for Advanced Studies & National Presto Industries.

The role of autophagy during the early neonatal starvation period

Abstract: At birth the trans-placental nutrient supply is suddenly interrupted, and neonates face severe starvation until supply can be restored through milk nutrients. Here, we show that neonates adapt to this adverse circumstance by inducing autophagy. Autophagy is the primary means for the degradation of cytoplasmic constituents within lysosomes. The level of autophagy in mice remains low during embryogenesis; however, autophagy is immediately upregulated in various tissues after birth and is maintained at high levels for 3-12 h before returning to basal levels within 1-2 days. Mice deficient for Atg5, which is essential for autophagosome formation, appear almost normal at birth but die within 1 day of delivery. The survival time of starved Atg5-deficient neonates (approximately 12 h) is much shorter than that of wild-type mice (approximately 21 h) but can be prolonged by forced milk feeding. Atg5-deficient neonates exhibit reduced amino acid concentrations in plasma and tissues, and display signs of energy depletion. These results suggest that the production of amino acids by autophagic degradation of 'self' proteins, which allows for the maintenance of energy homeostasis, is important for survival during neonatal starvation.

Mouse Apg16L, a novel WD-repeat protein, targets to the autophagic isolation membrane with the Apg12-Apg5 conjugate

Abstract: Macroautophagy is the major intracellular degradation system delivering cytoplasmic components to the lysosome/vacuole. We have shown that, in yeast and mammalian cells, the Apg12-Apg5 protein conjugate, which is formed by a ubiquitin-like system, is essential for autophagosome formation. In yeast, the Apg12-Apg5 conjugate interacts with a small coiled-coil protein, Apg16, to form a approximately 350 kDa multimeric complex. We demonstrate that the mouse Apg12-Apg5 conjugate forms a approximately 800 kDa protein complex containing a novel WD-repeat protein. Because the N-terminal region of this novel protein shows homology with yeast Apg16, we have designated it mouse Apg16-like protein (Apg16L). Apg16L, however, has a large C-terminal domain containing seven WD repeats that is absent from yeast Apg16. Apg16L interacts with both Apg5 and additional Apg16L monomers; neither interaction, however, depends on the WD-repeat domain. In conjunction with Apg12-Apg5, Apg16L associates with the autophagic isolation membrane for the duration of autophagosome formation. Because these features are similar to yeast Apg16, we concluded Apg16L is the functional counterpart of the yeast Apg16. We also found that membrane targeting of Apg16L requires Apg5 but not Apg12. Because WD-repeat proteins provide a platform for protein-protein interactions, the approximately 800 kDa complex is expected to function in autophagosome formation, further interacting with other proteins in mammalian cells.

LC3, an autophagosome marker, can be incorporated into protein aggregates independent of autophagy: caution in the interpretation of LC3 localization.

Abstract: Autophagy is an intracellular bulk degradation system, through which a portion of the cytoplasm is delivered to lysosomes to be degraded. Microtuble-associated protein light chain 3 (LC3), a mammalian homolog of yeast Atg8, has been used as a specific marker to monitor autophagy. Upon induction of autophagy, LC3 is conjugated to phosphatidylethanolamine and targeted to autophagic membranes. Therefore, changes in LC3 localization have been used to measure autophagy. However, this method has some limitations. In this report, we show that LC3 protein tends to aggregate in an autophagy-independent manner when it is transiently overexpressed by transfection. In addition, LC3 is easily incorporated into intracellular protein aggregates, such as inclusion bodies induced by polyQ expression or formed in autophagy-deficient hepatocytes, neurons, or senescent fibroblasts. These findings demonstrate that punctate dots containing LC3 do not always represent autophagic structures. Therefore, LC3 localization should be...

Autophagy Is Essential for Preimplantation Development of Mouse Embryos

Abstract: After fertilization, maternal proteins in oocytes are degraded and new proteins encoded by the zygotic genome are synthesized. We found that autophagy, a process for the degradation of cytoplasmic constituents in the lysosome, plays a critical role during this period. Autophagy was triggered by fertilization and up-regulated in early mouse embryos. Autophagy-defective oocytes derived from oocyte-specific Atg5 (autophagy-related 5) knockout mice failed to develop beyond the four- and eight-cell stages if they were fertilized by Atg5-null sperm, but could develop if they were fertilized by wild-type sperm. Protein synthesis rates were reduced in the autophagy-null embryos. Thus, autophagic degradation within early embryos is essential for preimplantation development in mammals.

Autophagy fights disease through cellular self-digestion

Abstract: Autophagy, or cellular self-digestion, is a cellular pathway involved in protein and organelle degradation, with an astonishing number of connections to human disease and physiology. For example, autophagic dysfunction is associated with cancer, neurodegeneration, microbial infection and ageing. Paradoxically, although autophagy is primarily a protective process for the cell, it can also play a role in cell death. Understanding autophagy may ultimately allow scientists and clinicians to harness this process for the purpose of improving human health.

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.