Regulatory interactions in the recognition of endocytic sorting signals by AP-2 complexes.
Many plasma membrane proteins destined for endocytosis are concentrated into clathrin-coated pits through the recognition of a tyrosine-based motif in their cytosolic domains by an adaptor (AP-2) complex. The mu2 subunit of isolated AP-2 complexes binds specifically, but rather weakly, to proteins bearing the tyrosine-based signal. We now demonstrate, using peptides with a photoreactive probe, that this binding is strengthened significantly when the AP-2 complex is present in clathrin coats, indicating that there is cooperativity between receptor-AP-2 interactions and coat formation. Phosphoinositides with a phosphate at the D-3 position of the inositol ring, but not other isomers, also increase the affinity of the AP-2 complex for the tyrosine-based motif. AP-2 is the first protein known (in any context) to interact with phosphatidylinositol 3-phosphate. Our findings indicate that receptor recruitment can be coupled to clathrin coat assembly and suggest a mechanism for regulation of membrane traffic by lipid products of phosphoinositide 3-kinases.
Rapoport
I
I
Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Miyazaki
M
M
Boll
W
W
Duckworth
B
B
Cantley
L C
LC
Shoelson
S
S
Kirchhausen
T
T
D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033963:Adaptor Protein Complex 3; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis; D006023:Glycoproteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
C510070:AP3M2 protein, human; D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033963:Adaptor Protein Complex 3; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D002966:Clathrin; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D021382:Protein Sorting Signals; C499065:adaptor protein complex 1, mu 2 subunit; C438886:adaptor protein complex 2, mu 2 subunit; D014443:Tyrosine; D000409:Alanine