title: Two types of transmembrane homomeric interactions in the integrin receptor family are evolutionarily conserved.
abstract: Integrins are heterodimers, but recent in vitro and in vivo experiments suggest that they are also able to associate through their transmembrane domains to form homomeric interactions. Two fundamental questions are the biological relevance of these aggregates and their form of interaction in the membrane domain. Although in vitro experiments have shown the involvement of a GxxxG-like motif, several crosslinking in vivo data are consistent with an almost opposite form of interaction between the transmembrane alpha-helices. In the present work, we have explored these two questions using molecular dynamics simulations for all available integrin types. We have tested the hypothesis that homomeric interactions are evolutionary conserved, and essential for the cell, using conservative substitutions to filter out nonnative interactions. Our results show that two models, one involving a GxxxG-like motif (model I) and an almost opposite form of interaction (model II) are conserved across all alpha and beta integrin types, both in homodimers and homotrimers, with different specificities. No conserved interaction was found for homotetramers. Our results are completely independent from experimental data, both during molecular dynamics simulations and in the selection of the correct models. We rationalize previous seemingly conflicting findings regarding the nature of integrin interhelical homomeric interactions.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 637551, Singapore.
authors.forename: Xin
authors.initials: X
authors.lastname: Lin
authors.forename: Suet Mien
authors.initials: SM
authors.lastname: Tan
authors.forename: S K Alex
authors.initials: SK
authors.lastname: Law
authors.forename: Jaume
authors.initials: J
authors.lastname: Torres
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019295:Computational Biology / Q000379:methods*; D017124:Conserved Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019281:Dimerization; D019143:Evolution, Molecular; D006801:Humans; D039001:Integrin alpha Chains / Q000737:chemistry; D039641:Integrin beta Chains / Q000737:chemistry; D016023:Integrins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods*; D017386:Sequence Homology, Amino Acid
chemical_list: D003432:Cross-Linking Reagents; D039001:Integrin alpha Chains; D039641:Integrin beta Chains; D016023:Integrins