A novel GGA-binding site is required for intracellular sorting mediated by stabilin-1.
Stabilin-1 is a unique scavenger receptor that combines endocytic and intracellular sorting functions in macrophages. Stabilin-1 mediates the endocytosis of acetylated low-density lipoprotein (acLDL), SPARC, and growth hormone family member placental lactogen (PL). At the same time, stabilin-1 is involved in trans-Golgi network-to-endosome routing of the endogenous chitinase-like protein SI-CLP (stabilin-interacting chitinase-like protein). A DDSLL motif in the cytoplasmic tail of stabilin-1 interacts with GGA adaptors; however, the deletion of DDSLL reduces but does not abrogate this interaction. Here, we identified a novel GGA-binding site, EDDADDD, in the cytoplasmic tail of stabilin-1. The deletion of EDDADDD impaired and the deletion of both the DDSLL and EDDADDD sites abrogated the interaction of stabilin-1 with GGAs. The surface exposure of stabilin-1 and stabilin-1-mediated endocytosis of acLDL, SPARC, and PL were not affected by the deletion either of DDSLL or EDDADDD or both. At the same time, both GGA-binding sites were necessary for the intracellular sorting of SI-CLP performed by stabilin-1. Our data indicate that the novel GGA-binding site EDDADDD is essential for stabilin-1-mediated intracellular sorting but is not required for endocytosis.
Zhang
Jingjing
J
Medical Faculty Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167 Mannheim, Germany.
Gratchev
Alexei
A
Riabov
Vladimir
V
Mamidi
Srinivas
S
Schmuttermaier
Christina
C
Krusell
Liis
L
Kremmer
Elisabeth
E
Workman
Gail
G
Sage
E Helene
EH
Jalkanen
Sirpa
S
Goerdt
Sergij
S
Kzhyshkowska
Julia
J
D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis; D005456:Fluorescent Dyes; D042541:Intracellular Space / Q000378:metabolism*; D008969:Molecular Sequence Data; D021381:Protein Transport; D016201:Receptors, Lymphocyte Homing / Q000737:chemistry* / Q000378:metabolism*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
D033942:Adaptor Proteins, Vesicular Transport; D015816:Cell Adhesion Molecules, Neuronal; D005456:Fluorescent Dyes; C407306:GGA adaptor proteins; D016201:Receptors, Lymphocyte Homing; C449926:STAB1 protein, human