Identification of a motif in the carboxyl terminus of CXCR2 that is involved in adaptin 2 binding and receptor internalization

Agonist treatment of cells expressing the chemokine receptor, CXCR2, induce s receptor phosphorylation and internalization through a dynamin-dependent mechanism. In the present study, we demonstrate that a carboxyl terminus-tr uncated mutant of CXCR2 (331T), which no longer undergoes agonist-induced p hosphorylation, continues to undergo ligand-induced internalization in HEK2 93 cells. This mutant receptor exhibits reduced association with beta -arre stin 1 but continues to exhibit association with adaptin 2 alpha and beta s ubunits. Replacing Leu320-321 and/or Ile323-Leu324 with Ala (LL320,321AA, I L323,324AA, and LLIL320,321,323,324AAAA) in wild-type CXCR2 or 331T causes little change in ligand binding and signaling through Ca2+ mobilization but greatly impairs the agonist-induced receptor sequestration and ligand-medi ated chemotaxis. The LL320,321AA. IL323.324AA, and LLIL320,321,323,324AAAA mutants of CXCR2 exhibit normal binding to beta -arrestin 1 but exhibit dec reased binding to adaptin 2 alpha and beta. These data demonstrate a role f or the LLKIL motif in the carboxyl terminus of CXCR2 in receptor internaliz ation and cell chemotaxis and imply a role for adaptin 2 in the endocytosis of CXCR2.