Identification of an endocytosis motif in an intracellular loop of Wntless protein, essential for its recycling and the control of Wnt protein signaling.
The secretion of Wnt signaling proteins is dependent upon the transmembrane sorting receptor, Wntless (Wls), which recycles between the trans-Golgi network and the cell surface. Loss of Wls results in impairment of Wnt secretion and defects in development and homeostasis in Drosophila, Caenorhabditis elegans, and the mouse. The sorting signals for the internalization and trafficking of Wls have not been defined. Here, we demonstrate that Wls internalization requires clathrin and dynamin I, components of the clathrin-mediated endocytosis pathway. Moreover, we have identified a conserved YXXϕ endocytosis motif in the third intracellular loop of the multipass membrane protein Wls. Mutation of the tyrosine-based motif YEGL to AEGL (Y425A) resulted in the accumulation of human mutant Wls on the cell surface of transfected HeLa cells. The cell surface accumulation of Wls(AEGL) was rescued by the insertion of a classical YXXϕ motif in the cytoplasmic tail. Significantly, a Drosophila Wls(AEGL) mutant displayed a wing notch phenotype, with reduced Wnt secretion and signaling. These findings demonstrate that YXXϕ endocytosis motifs can occur in the intracellular loops of multipass membrane proteins and, moreover, provide direct evidence that the trafficking of Wls is required for efficient secretion of Wnt signaling proteins.
Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
Isabelle
I
Gasnereau
Patrick
P
Herr
Pei Zhi Cheryl
PZ
Chia
Konrad
K
Basler
Paul A
PA
Gleeson
D020816:Amino Acid Motifs; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*
D002966:Clathrin; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; C549111:WLS protein, human; D051153:Wnt Proteins