title: Sequential steps of macroautophagy and chaperone-mediated autophagy are involved in the irreversible process of posterior silk gland histolysis during metamorphosis of Bombyx mori.
abstract: To elucidate the degradation process of the posterior silk gland during metamorphosis of the silkworm ITALIC! Bombyx mori, tissues collected on the 6th day after entering the 5th instar (V6), prior to spinning (PS), during spinning (SP) and after cocoon formation (CO) were used to analyze macroautophagy, chaperone-mediated autophagy (CMA) and the adenosine triphosphate (ATP)-dependent ubiquitin proteasome. Immediately after entering metamorphosis stage PS, the levels of ATP and phosphorylated p70S6 kinase protein decreased spontaneously and continued to decline at SP, followed by a notable restoration at CO. In contrast, phosphorylated AMP-activated protein kinase α (AMPKα) showed increases at SP and CO. Most of the Atg8 protein was converted to form II at all stages. The levels of ubiquitinated proteins were high at SP and CO, and low at PS. The proteasome activity was high at V6 and PS but low at SP and CO. In the isolated lysosome fractions, levels of Hsc70/Hsp70 protein began to increase at PS and continued to rise at SP and CO. The lysosomal cathepsin B/L activity showed a dramatic increase at CO. Our results clearly demonstrate that macroautophagy occurs before entering the metamorphosis stage and strongly suggest that the CMA pathway may play an important role in the histolysis of the posterior silk gland during metamorphosis.
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan chang@brs.nihon-u.ac.jp.
authors.forename: Hajime
authors.initials: H
authors.lastname: Shiba
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yabu
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Sudayama
authors.affiliation: Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mano
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Arai
authors.affiliation: Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan.
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Hosono
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000825:Animal Structures / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000071182:Autophagosomes / Q000187:drug effects / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D012831:Bombyx / Q000033:anatomy & histology* / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000032:analysis; D006458:Hemolymph / Q000187:drug effects / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism; D007814:Larva / Q000187:drug effects; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000187:drug effects; D018832:Molecular Chaperones / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D009997:Osmotic Pressure / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D047011:Silk / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D018832:Molecular Chaperones; D047011:Silk; D025801:Ubiquitin; D000255:Adenosine Triphosphate; D046988:Proteasome Endopeptidase Complex; D005947:Glucose
keywords: Atg8; Cathepsin B/L; Degradation; Histolysis; Hsc70/Hsp70; Lysosome; Silkworm