HM1.24 is internalized from lipid rafts by clathrin-mediated endocytosis through interaction with alpha-adaptin.
HM1.24/Bst2/CD317 is a protein highly expressed in multiple myeloma cells and has unique topology with two membrane anchor domains, an NH2-terminal transmembrane domain and a glycosylphosphatidylinositol attached to the COOH terminus. We show here that human HM1.24 is localized not only on the cell surface but also in the trans-Golgi network and/or recycling endosomes, where it resides in detergent-resistant microdomains, lipid rafts. In contrast to other glycosylphosphatidylinositol-anchored proteins, HM1.24 was internalized from lipid rafts on the cell surface by clathrin-mediated endocytosis. Interestingly, a non-canonical tyrosine-based motif, which contains two tyrosine residues, Tyr-6 and Tyr-8, present in the NH2-terminal cytoplasmic tail, was essential for endocytosis through interaction with an Deltaa-adaptin, but not mu2-subunit, of the AP-2 complex. Indeed, an appendage domain of alpha-adaptin was identified as a protein interacting with the cytoplasmic tail of HM1.24. Furthermore, overexpression of the appendage domain of alpha-adaptin in cells depleted of alpha-adaptin could rescue the clathrin-mediated endocytosis of HM1.24 but not of the transferrin receptor. Taken together, our findings suggest that clathrin-dependent endocytosis of human HM1.24 from the cell surface lipid rafts is mediated by direct interaction with alpha-adaptin.
Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka 812-8582, Japan.
Naoko
N
Masuyama
Toshio
T
Kuronita
Rika
R
Tanaka
Tomonori
T
Muto
Yuko
Y
Hirota
Azusa
A
Takigawa
Hideaki
H
Fujita
Yoshinori
Y
Aso
Jun
J
Amano
Yoshitaka
Y
Tanaka
D033965:Adaptor Protein Complex alpha Subunits / Q000502:physiology*; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology*; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology; D058851:GPI-Linked Proteins; D005784:Gene Amplification; D006367:HeLa Cells / Q000502:physiology; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D021962:Membrane Microdomains / Q000502:physiology*; D009101:Multiple Myeloma / Q000503:physiopathology; D016133:Polymerase Chain Reaction; D020298:U937 Cells; D021601:trans-Golgi Network / Q000502:physiology; D000074010:Bone Marrow Stromal Antigen 2
D033965:Adaptor Protein Complex alpha Subunits; D015703:Antigens, CD; D002966:Clathrin; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2