Leupeptin-Induced Appearance of Partial Fragment of Betaine Homocysteine Methyltransferase during Autophagic Maturation in Rat Hepatocytes

Furuya, Norihiko; Kanazawa, Takumi; Fujimura, Shigefumi; Ueno, Takashi; Kominami, Eiki; Kadowaki, Motoni

doi:10.1093/oxfordjournals.jbchem.a002859

Cited by 25 publications

(24 citation statements)

References 38 publications

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“…85 BHMT fragments of ∼32 (p32) and ∼35 kDa (p35) were previously shown to accumulate in mitochondrial-lysosomal (ML) subcellular fractions and autolysosomes from rat hepatocytes treated with leupeptin, an inhibitor of intralysosomal protein degradation. 86,87 Whereas p32 appeared to be generated intralysosomally from autophagocytosed BHMT, 87 p35 was associated with autolysosomal membranes 86 and might perhaps be related to the autophagosomal membrane-associated BHMT fragments found in the present study. Both p32 and larger BHMT fragments could be generated proteolytically in liver cell extracts, 86,87 but how BHMT is processed in intact cells is not known.…”

Section: Table 3 Sequence Alignment Of Comt Peptides Identified By Mamentioning

confidence: 59%

Proteomic Analysis of Membrane-Associated Proteins from Rat Liver Autophagosomes

Øverbye¹,

Fengsrud²,

Seglen³

2007

Autophagy

143

117

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Section: Table 3 Sequence Alignment Of Comt Peptides Identified By Mamentioning

confidence: 59%

Proteomic Analysis of Membrane-Associated Proteins from Rat Liver Autophagosomes

Øverbye¹,

Fengsrud²,

Seglen³

2007

Autophagy

143

117

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“…Moreover, BHMT fragments (p32 and p35) have been found to accumulate in mitochondrial-lysosomal subcellular fractions and autolysosomes from rat hepatocytes treated with leupeptin, an inhibitor of intralysosomal protein degradation. 35,36) These observations and reports suggest that TG is involved in the formation of autophagosome and/ or autolysosome.…”

Section: Discussionmentioning

confidence: 80%

Identification of New Amine Acceptor Protein Substrate Candidates of Transglutaminase in Rat Liver Extract: Use of 5-(Biotinamido) Pentylamine as a Probe

Ichikawa

Ishizaki

Morita

et al. 2008

Bioscience, Biotechnology, and Biochemistry

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Transglutaminases (TGs) are a family of enzymes that catalyze Ca 2þ -dependent post-translational modification of proteins by introducing protein-protein crosslinks (between specific glutamine and lysine residues), amine incorporation, and site-specific deamidation. In this study, new amine acceptor protein substrates of TG were isolated from rat liver extract and identified using 5-(biotinamido) pentylamine, a biotinylated primary amine substrate, as a probe. TG protein substrate candidates labeled with biotin by endogenous TG activity were isolated and recovered by avidin column chromatography. Proteins with molecular masses of 40, 42, and 45 kDa were the main components of the labeled proteins. Determination of their partial amino acid sequences and immunoblotting analyses were done to identify them. The 45-kDa protein was identical with betaine-homocysteine S-methyltransferase (EC 2.2.2.5), which was identified in our previous study. The 40-and 42-kDa proteins were identified as arginase-I (EC 3.5.3.1) and fructose-1,6-bisphosphatase (EC 3.1.3.11) respectively. TG catalyzed incorporation of 5-(biotinamido) pentylamine into both arginase-I and fructose-1,6-bisphosphatase purified from rat liver was confirmed in vitro. These results suggest that these two enzymes are the new protein substrate candidates of TG and that they can be modified post-translationally by cellular TG.

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“…However, 3-methyladenine inhibits not only Class III PI-3K but also Class I kinase, and the concentration required for effective inhibition is very high. Treatment with inhibitors such as leupeptin, a cathepsin inhibitor, induces the formation of many vacuoles containing various cytoplasmic enzymes by blocking degradation in the lysosome, and biochemical analysis revealed that these represent non-selective enwrapping of cytosolic enzymes [24].…”

Section: Before the Autophagy-related Genesmentioning

confidence: 99%

Historical landmarks of autophagy research

2013

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The year of 2013 marked the 50th anniversary of C de Duve's coining of the term "autophagy" for the degradation process of cytoplasmic constituents in the lysosome/vacuole. This year we regretfully lost this great scientist, who contributed much during the early years of research to the field of autophagy. Soon after the discovery of lysosomes by de Duve, electron microscopy revealed autophagy as a means of delivering intracellular components to the lysosome. For a long time after the discovery of autophagy, studies failed to yield any significant advances at a molecular level in our understanding of this fundamental pathway of degradation. The first breakthrough was made in the early 1990s, as autophagy was discovered in yeast subjected to starvation by microscopic observation. Next, a genetic effort to address the poorly understood problem of autophagy led to the discovery of many autophagy-defective mutants. Subsequent identification of autophagy-related genes in yeast revealed unique sets of molecules involved in membrane dynamics during autophagy. ATG homologs were subsequently found in various organisms, indicating that the fundamental mechanism of autophagy is well conserved among eukaryotes. These findings brought revolutionary changes to research in this field. For instance, the last 10 years have seen remarkable progress in our understanding of autophagy, not only in terms of the molecular mechanisms of autophagy, but also with regard to its broad physiological roles and relevance to health and disease. Now our knowledge of autophagy is dramatically expanding day by day. Here, the historical landmarks underpinning the explosion of autophagy research are described with a particular focus on the contribution of yeast as a model organism.

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Leupeptin-Induced Appearance of Partial Fragment of Betaine Homocysteine Methyltransferase during Autophagic Maturation in Rat Hepatocytes

Cited by 25 publications

References 38 publications

Proteomic Analysis of Membrane-Associated Proteins from Rat Liver Autophagosomes

Proteomic Analysis of Membrane-Associated Proteins from Rat Liver Autophagosomes

Identification of New Amine Acceptor Protein Substrate Candidates of Transglutaminase in Rat Liver Extract: Use of 5-(Biotinamido) Pentylamine as a Probe

Historical landmarks of autophagy research

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