Numb3 is an endocytosis adaptor for the inflammatory marker P-selectin.
The endocytic protein Numb3 was found to bind to the cytosolic tail of the leukocyte adhesion receptor P-selectin. The N-terminal phosphotyrosine-binding (PTB) domain of Numb3 is responsible for this activity. An alanine scan revealed the FTNAAFD sequence as recognition region in P-selectin. Structural modeling of the interaction between the Numb PTB domain and the P-selectin tail suggests that both phenylalanines within the recognition sequence fit into hydrophobic cavities of the PTB surface. Their exchange for alanine gave Numb-negative mutants detaining the inhibition of P-selectin endocytosis by Numb PTB overexpression. Cells stable expressing P-selectins internalized the negative mutants markedly slower than the wild type. Consistent with other reports on the phosphorylation of Numb, we found that only the dephospho-Numb is able to bind P-selectin. Our observations demonstrate that Numb3 is an endocytic receptor for P-selectin and may be responsible for the rapid internalization of P-selectin when endothelial activation ends.
Schlüter
Thomas
T
Institut für Biochemie und Zellbiologie, Medizinische Fakultät, Otto-von-Guericke-Universität Magdeburg, Leipziger Strasse 44, D-39120 Magdeburg, Germany. thomas.schlueter@med.ovgu.de
Knauth
Peter
P
Wald
Susan
S
Boland
Sabine
S
Bohnensack
Ralf
R
D017398:Alternative Splicing; D004705:Endocytosis; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019007:P-Selectin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C113026:NUMB protein, human; D019007:P-Selectin; D010649:Phenylalanine; D011494:Protein Kinases