A lactoferrin-receptor, intelectin 1, affects uptake, sub-cellular localization and release of immunochemically detectable lactoferrin by intestinal epithelial Caco-2 cells.
Intelectin 1 (IntL) is known as a lectin expressed in intestinal epithelia and also as a receptor for an iron-binding protein, lactoferrin (LF). Uptake of LF with bound iron by enterocytes via receptor-mediated endocytosis has been well investigated, whereas subsequent fate of endocytized LF and LF/IntL complexes remains largely unknown. In the present study, we examined contribution of IntL to the uptake, sub-cellular localization and subsequent release of LF by intestinal Caco-2 IntL-transfectants using two-site ELISA and fluorescence confocal microscopy. LF taken up by IntL-transfectants was immunochemically detected mostly as intact protein in the cell lysates, and it was a little larger in amount than that of the mock-transfectants. In the IntL-transfectants cultured on porous membrane, LF taken up from the apical side was detected immunochemically as punctate signals in the apical-side cytoplasmic region near nucleus. The LF signals were co-localized with IntL and, in a time-dependent manner, partially with early endosome antigen 1 (EEA1), but not with alkaline phosphatase. LF taken up, retained and subsequently released by the IntL-transfectants was larger in amount than that of mock-transfectants. Moreover, uptake of LF altered sub-cellular localization of IntL and markedly enhanced the IntL signals within the cells.
Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8601; and Food Science & Technology Institute, Morinaga Milk Industry Co., Ltd., 5-1-83 Higashihara, Zama, Kanagawa 228-8583, Japan.
Yuka
Y
Akiyama
Kenzi
K
Oshima
Tetsuya
T
Kuhara
Kouichirou
K
Shin
Fumiaki
F
Abe
Keiji
K
Iwatsuki
Daita
D
Nadano
Tsukasa
T
Matsuda
D018938:Caco-2 Cells; D016207:Cytokines / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism*; D058851:GPI-Linked Proteins / Q000378:metabolism; D006801:Humans; D007120:Immunochemistry; D007422:Intestines / Q000166:cytology; D007781:Lactoferrin / Q000032:analysis / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence
D016207:Cytokines; D058851:GPI-Linked Proteins; C432397:ITLN1 protein, human; D037102:Lectins; D007781:Lactoferrin
intestinal protein absorption; protein sorting; protein transcytosis; receptor-mediated endocytosis; sub-cellular protein degradation