Structural basis of the dynamic human CEACAM1 monomer-dimer equilibrium

Abstract

Human (h) carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) function depends upon IgV-mediated homodimerization or heterodimerization with host ligands, including hCEACAM5, hTIM-3, PD-1, and a variety of microbial pathogens. However, there is little structural information available on how hCEACAM1 transitions between monomeric and dimeric states which in the latter case is critical for initiating hCEACAM1 activities. We therefore mutated residues within the hCEACAM1 IgV GFCC′ face including V39, I91, N97, and E99 and examined hCEACAM1 IgV monomer-homodimer exchange using differential scanning fluorimetry, multi-angle light scattering, X-ray crystallography and/or nuclear magnetic resonance. From these studies, we describe hCEACAM1 homodimeric, monomeric and transition states at atomic resolution and its conformational behavior in solution through NMR assignment of the wildtype (WT) hCEACAM1 IgV dimer and N97A mutant monomer. These studies reveal the flexibility of the GFCC’ face and its important role in governing the formation of hCEACAM1 dimers and selective heterodimers.

Multi-omics integration and interactomics reveals molecular networks and regulators of the beneficial effect of yoga and exercise

“…[ 73 ] The protein encoded by CEACAM1 have been attributed has been attributed with multiple functions including roles in the differentiation and arrangement of tissue three-dimensional structure, angiogenesis, apoptosis, tumor suppression, and the modulation of innate and adaptive immune responses. [ 74 ]…”

An investigation into the role of inherited CEACAM gene family variants and colorectal cancer risk

“…These results were unexpected due to the previous association of rare PTVs in the CEACAM gene family with inherited breast cancer risk [ 16 ], the known similarities between breast cancer and CRC risk [ 1 , 17 , 18 ], and the dis-regulation of CEACAM genes in CRC tumors [ 6 , 8 – 15 ]. Moreover, it has been demonstrated that CEACAM gene function can be affected by even minor genetic changes [ 27 ], and specific residues within CEACAM proteins are crucial for normal function [ 12 , 30 , 31 ].…”

“…The Ig V-set domain is crucial for the dimerization of many CEACAM proteins and their ability to function within normal ranges [ 31 , 32 ]. In CEACAM1, mutating particular residues within the Ig V-set domain can affect the monomer-homodimer exchange and result in the protein staying in a monomeric state [ 31 ]. CEACAM1’s ability to dimerize is required for proper function [ 33 – 36 ].…”

Structural analysis of human CEACAM1 oligomerization

“…In addition, IgV-like N-domain containing secreted isoforms also exist 2 . Like other hCEACAM family members, the hCEACAM1 IgV domain serves as the major ligand binding surface and is characterized by the presence of two anti-parallel β-sheets creating two distinct faces, the GFCC′ and ABED faces, respectively 7 – 9 .…”

“…The major mode of hCEACAM1 binding is homophilic such that it exists on the cell surface as collections of monomers and cis-dimers. This monomer:dimer equilibrium is mainly determined by interactions between the GFCC’ faces of the IgV domains of opposing hCEACAM1 molecules, residues within the transmembrane domain and intracellular calcium concentrations mediated by cellular activation where increased calcium levels promotes hCEACAM1 monomerization 1 , 2 , 7 , 10 . The formation of cell surface hCEACAM1 monomers allows for trans-homophilic or heterophilic interactions critical to the induction of biologic responses 1 , 2 , 7 , 10 .…”