Structural requirements for the interaction of human IgM and IgA with the human Fc alpha/mu receptor

TY - JOUR

T1 - Structural requirements for the interaction of human IgM and IgA with the human Fc alpha/mu receptor

AU - Ghumra, Ashfaq

AU - Shi, Jianguo

AU - Mcintosh, Richard S.

AU - Rasmussen, Ingunn B.

AU - Braathen, Ranveig

AU - Johansen, Finn-Eirik

AU - Sandlie, Inger

AU - Mongini, Patricia K.

AU - Areschoug, Thomas

AU - Lindahl, Gunnar

AU - Lewis, Melanie J.

AU - Woof, Jennifer M.

AU - Pleass, Richard J.

PY - 2009/4

Y1 - 2009/4

N2 - Here we unravel the structural features of human IgM and IgA that govern their interaction with the human Fc alpha/mu receptor (hFc alpha/mu R). Ligand polymerization status was crucial for the interaction, because hFc alpha/mu R binding did not occur with monomeric Ab of either class. hFc alpha/mu R bound IgM with an affinity in the nanomolar range, whereas the affinity for dimeric IgA (dIgA) was tenfold lower. Panels of mutant IgM and dIgA were used to identify regions critical for hFc alpha/mu R binding. IgM binding required contributions from both C mu 3 and C mu 4 Fc domains, whereas for dIgA, an exposed loop in the C alpha 3 domain was crucial. This loop, comprising residues Pro440-Phe443, lies at the Fc domain interface and has been implicated in the binding of host receptors Fc alpha RI and polymeric Ig receptor (pIgR), as well as IgA-binding proteins produced by certain pathogenic bacteria. Substitutions within the Pro440-Phe443 loop resulted in loss of hFc alpha/mu R binding. Furthermore, secretory component (SC, the extracellular portion of pIgR) and bacterial IgA-binding proteins were shown to inhibit the dIgA-hFc alpha/mu R interaction. Therefore, we have identified a motif in the IgA-Fc inter-domain region critical for hFc alpha/mu R interaction, and highlighted the multi-functional nature of a key site for protein-protein interaction at the IgA Fc domain interface.

AB - Here we unravel the structural features of human IgM and IgA that govern their interaction with the human Fc alpha/mu receptor (hFc alpha/mu R). Ligand polymerization status was crucial for the interaction, because hFc alpha/mu R binding did not occur with monomeric Ab of either class. hFc alpha/mu R bound IgM with an affinity in the nanomolar range, whereas the affinity for dimeric IgA (dIgA) was tenfold lower. Panels of mutant IgM and dIgA were used to identify regions critical for hFc alpha/mu R binding. IgM binding required contributions from both C mu 3 and C mu 4 Fc domains, whereas for dIgA, an exposed loop in the C alpha 3 domain was crucial. This loop, comprising residues Pro440-Phe443, lies at the Fc domain interface and has been implicated in the binding of host receptors Fc alpha RI and polymeric Ig receptor (pIgR), as well as IgA-binding proteins produced by certain pathogenic bacteria. Substitutions within the Pro440-Phe443 loop resulted in loss of hFc alpha/mu R binding. Furthermore, secretory component (SC, the extracellular portion of pIgR) and bacterial IgA-binding proteins were shown to inhibit the dIgA-hFc alpha/mu R interaction. Therefore, we have identified a motif in the IgA-Fc inter-domain region critical for hFc alpha/mu R interaction, and highlighted the multi-functional nature of a key site for protein-protein interaction at the IgA Fc domain interface.

KW - Human Fc alpha/mu receptor

KW - IgA

KW - IgM

KW - POLYMERIC IMMUNOGLOBULIN RECEPTOR

KW - J-CHAIN

KW - BINDING-SITE

KW - EPITHELIAL TRANSPORT

KW - DOMAIN

KW - PROTEINS

KW - ANTIBODIES

KW - INTERFACE

KW - REGION

KW - CD89

UR - https://www.scopus.com/pages/publications/65449156532

U2 - 10.1002/eji.200839184

DO - 10.1002/eji.200839184

M3 - Article

C2 - 19266484

SN - 0014-2980

VL - 39

SP - 1147

EP - 1156

JO - European Journal of Immunology

JF - European Journal of Immunology

IS - 4

ER -