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Involvement of macroautophagy and chaperone‐mediated autophagy in the irreversible process of posterior silk gland histolysis during metamorphosis of Bombyx mori
Author(s) -
Shiba Hajime,
Yabu Takeshi,
Kawabe Ryousuke,
Mano Nobuhiro,
Nakanishi Truyuki
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.906.3
Subject(s) - metamorphosis , autophagy , cathepsin d , bombyx mori , chemistry , western blot , endocrinology , medicine , cathepsin , microbiology and biotechnology , biology , biochemistry , enzyme , larva , ecology , apoptosis , gene
As an approach to clarify the physiological condition and events occurring during the silk gland histolysis, western blot analysis were performed in addition to measuring the glucose level in body fluid and the lysosomal cathepsin activity at different stages, i.e. 6th day after entering 5 th instar (V 6 ), prior to spinning (PS), during spinning (S), after cocoon formation (C). The levels of glucose in the body fluid and the phosphorylated p70S6Kinase, which were high at the V 6 stage, decreased dramatically after entering metamorphosis at the PS stage, reached the lowest level at the S stage and increased slightly at the C stage. The phosphorylated form of AMPKalpha became detectable at the S stages and increased remarkably at the C stage. The atg8 protein was detected at the stages of V 6 , PS and S, indicating that macroautophagy occurred before entering the metamorphosis stage and ended before completion of cocoon formation. The lysosomal cathepsin B/L activity showed a dramatic increase at the C stage; it was low at the stages of V 6 , PS and S. Regarding the ubiqutinated proteins level, it increased remarkably at the stages of S and C. These results suggest that chaperon‐mediated autophagy is involved in the silk gland degradation as well. In conclusion, our results reveal that the shift of the physiological condition at the PS stage allows the catabolic process to be promoted irreversibly.