Identification of amino acids involved in the binding of hMIP-1[alpha] to CC-CKR1, a MIP-l[alpha] receptor found on neutrophils

Human macrophage inflammatory protein-1α (hMIP-1α) and human macrophage inflammatory protein-1β (hMIP-1β) are chemokines involved in a diverse range of immunological effects. Both hMIP-1α and hMIP-1β are involved in the activation of monocytes and THP-1 cells probably through a common receptor(s). However, only hMIP-1α can bind to neutrophils with high affinity, presumably through CC-CKR1 (CKR1). Since the structure of these two proteins is highly conserved, non-conserved amino acids must define the disparate binding patterns that these two proteins exhibit. Measurements of binding, chemotaxis and calcium influx conducted with hMIP-1α and hMIP-1β chimeric proteins and mutants show that two amino acids (37K and 43L) are important in the binding and signaling of hMIP-1α through CKR1. Furthermore, we also show that mutations of the three charged amino acids at the C-terminus of hMIP-1α and hMIP-1β (amino acids 61, 65 and 67), do not adversely affect the binding to THP-1 cells.[PUBLICATION ABSTRACT]