Recombinant Mouse AMICA Fc Chimera Protein, CF

AMICA, also known as JAML, is a 65 kDa, type I transmembrane glycoprotein that belongs to the junctional adhesion molecule (JAM) subset of the immunoglobulin superfamily (1). JAM family proteins contribute to intercellular connections within epithelial and endothelial cell layers and mediate their interactions with various hemopoietic cells (1). The mouse AMICA cDNA encodes a 379 amino acid (aa) precursor that includes a 20 aa signal sequence, a 261 aa extracellular domain (ECD) with two Ig-like domains, a 21 aa transmembrane segment, and a 77 aa cytoplasmic domain (2). In contrast to other JAM family proteins, AMICA does not contain a cytoplasmic PDZ-binding motif (3). Within the ECD, mouse AMICA shares 58% and 77% aa sequence identity with human and rat AMICA, respectively. It shares 17% - 23% aa sequence identity with the ECDs of mouse JAM-A, -B, -C, and JAM4. AMICA is expressed on the surface of granulocytes and monocytes and is upregulated during the differentiation of myeloid leukemia cells (2, 3). A motif in the ECD, which promotes dimerization of other JAM family proteins, is required for surface localization of AMICA (2). AMICA mediates adhesion of monocytes to endothelial cells (2) and neutrophil migration across epithelial cell monolayers (3). This latter function involves specific interactions of AMICA with CXADR in epithelial tight junctions (3). In particular, the membrane proximal Ig-like domain of AMICA binds the membrane-distal Ig-like domain of CXADR (3). AMICA does not appear to interact homophilically, as neutrophils adhere to immobilized CXADR but not to immobilized AMICA (3).