title: Cathepsin C propeptide interacts with intestinal alkaline phosphatase and heat shock cognate protein 70 in human Caco-2 cells.
abstract: The oligomeric structure and the residual propeptide are distinct characteristics of cathepsin C from other members in the papain superfamily. In this study, we examined the physiological role of the cathepsin C propeptide. The stable overexpression of cathepsin C propeptide significantly decreased the activities of intestinal alkaline phosphatase (IAP) and sucrase in human Caco-2 intestinal epithelial cells, whereas it did not change the proliferation and cathepsin C activity. The overexpression of cathepsin C propeptide significantly decreased the amounts of IAP protein in differentiated Caco-2 cells, compared with the transfection of mock vector, whereas the amounts of IAP transcripts were not changed. Pulse-chase analysis confirmed that the reduction in IAP activity was due to an increase in IAP degradation, but not a decrease in IAP expression. For the mechanism of the enhanced IAP degradation, we identified proteins interacting with cathepsin C propeptide in Caco-2 cells by immunoprecipitation and mass spectrometry. Cathepsin C propeptide interacted with proteins with a molecular mass of approximately 70 kDa, including IAP and heat shock cognate protein 70. Our present results suggest that the propeptide of cathepsin C may stimulate the sorting to the lysosome, at least in part, contributing to the degradation of IAP in Caco-2 cells.
authors.affiliation: Department of Nutritional Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Hirasaka
authors.forename: Kaori
authors.initials: K
authors.lastname: Tokuoka
authors.forename: Reiko
authors.initials: R
authors.lastname: Nakao
authors.forename: Chiharu
authors.initials: C
authors.lastname: Yamada
authors.forename: Motoko
authors.initials: M
authors.lastname: Oarada
authors.forename: Takahito
authors.initials: T
authors.lastname: Imagawa
authors.forename: Kazumi
authors.initials: K
authors.lastname: Ishidoh
authors.forename: Yuushi
authors.initials: Y
authors.lastname: Okumura
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Kishi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nikawa
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000469:Alkaline Phosphatase; D000951:Antigens, Neoplasm / Q000378:metabolism*; D018938:Caco-2 Cells; D020789:Cathepsin C; D002403:Cathepsins / Q000378:metabolism*; D002454:Cell Differentiation; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D004792:Enzyme Precursors / Q000378:metabolism*; D058851:GPI-Linked Proteins; D015972:Gene Expression Regulation, Neoplastic; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D004792:Enzyme Precursors; D058851:GPI-Linked Proteins; D050883:HSC70 Heat-Shock Proteins; C063088:ALPI protein, human; D000469:Alkaline Phosphatase; D013393:Sucrase; D002403:Cathepsins; C533918:CTSC protein, human; D020789:Cathepsin C; C043569:cathepsin J