Uncoating ATPase Hsc70 is recruited by invariant chain and controls the size of endocytic compartments.
Targeting of class II major histocompatibility complex molecules to endocytic compartments is mediated by their association with the invariant chain (Ii). Although the identity of certain sorting signals located in Ii's cytoplasmic tail is known, proteins that interact with Ii's cytoplasmic tail in living cells remain to be identified. Synthesis of a biotinylated trimeric Ii cytoplasmic tail allowed the retrieval of two proteins that interact with this domain. We identify one of them as the 70-kDa heat-shock cognate protein (hsc70), the uncoating ATPase of clathrin-coated vesicles, and the other as its mitochondrial homologue, the glucose-regulated protein grp75. Expression of Ii in COS cells results in the formation of large endocytic compartments. We observe extensive colocalization of hsc70 with Ii in these macrosomes. Expression of a dominant-negative (K71M) green fluorescent protein-tagged version of hsc70 counteracted the ability of Ii to modify the endocytic pathway, demonstrating an interaction in vivo of Ii with hsc70 as part of the machinery responsible for macrosome formation.
Lagaudrière-Gesbert
Cécile
C
Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
Newmyer
Sherri L
SL
Gregers
Tone F
TF
Bakke
Oddmund
O
Ploegh
Hidde L
HL
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D015703:Antigens, CD / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002522:Chlorocebus aethiops; D004705:Endocytosis / Q000276:immunology*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006681:HLA-D Antigens / Q000276:immunology; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D011817:Rabbits; D014162:Transfection
D000906:Antibodies; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D002352:Carrier Proteins; D006681:HLA-D Antigens; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D000949:Histocompatibility Antigens Class II; D008164:Luminescent Proteins; C045084:invariant chain; D049452:Green Fluorescent Proteins