Rapid “mix-n-match” evolution of a housekeeping protein in response to bacterial antagonism EmilyClare Baker ¹, Kristin Kohler¹, Matt Barber¹ ¹University of Oregon Institute of Ecology and Evolution Based on PAML⁵ analysis of CEACAM proteins from 19 hominid, Old World Monkey and New World Monkey primates. The CEACAM protein family⁴ A multifunctional cell adhesion family in vertebrates N domain (IgV-like) IgC2-like domains* TM Cytoplasmic domain protein-protein binding domain includes ITIMs and other signaling motifs* (*presence and composition variable) *Number varies from 0 to 6 between different proteins and isoforms CEACAM protein domain structure Several bound by bacteria • CEACAM1 • CEACAM5 (CEA) • CEACAM6 • CEACAM3 Functions include... • Cell adhesion • Intra- and Intercellular signaling • Immune function • Cell cycle modulation CEACAMs 1, 5 & 6 • strong markers of cancer progression and prognosis • expressed on epithelia (esp. gastric) and immune cells • housekeeping proteins involved in cellular signaling CEACAM3 • expressed on immune cells • likely a dedicated immune protein Region bound by bacterial adhesins CEACAMs bound by bacterial adhesins the most rapidly evolving in primates • niche construction • immune evasion Bacterial adhesin proteins can exploit cell surface proteins for...⁴ • movement through the host Potentially decreasing host fitness bacterial adhesin – host protein interactions Consequences of evolutionary conflict between pathogens and host ‘housekeeping genes’ • Pathogen antagonism is predicted to lead to an ‘evolutionary arms race’ – characterized by rapid evolution host and bacterial proteins. Model of bacterial adhesin host protein evolutionary arms race 1 Bacterial adhesin is unable to bind to the host epithelial protein 2 Pressure to manipulate host drives evolution of bacterial adhesin to bind host protein 3 Pressure to prevent exploitation favors evolution of host protein away from adhesin binding 4 Pressure to evolve shifts back to the bacterial adhesin If and how housekeeping genes can evolve against pathogen exploitation is unclear. How host ‘housekeeping’ proteins can evolve to evade pathogen exploitation and maintain essential functions is an open question. Sites under selection are concentrated in the N-domains* domain targeted by bacterial adhesins * based on NS-sites analysis in PAML HopQ CEACAM1 N-domain Some sites under selection localize to interface with H. pylori HopQ Highlighted sites indicated as under selection by phylogenetic analysis programs PAML, FEL⁶ and MEME⁷ Bonobo CEACAM1 N-domain is unable to bind HopQ and has unusually divergend protein sequence 1. Correa P, Piazuelo MB. Evolutionary history of the Helicobacter pylori genome: Implications for gastric carcinogenesis. Gut Liver. 2012;6: 21–28. doi:10.5009/gnl.2012.6.1.21 2. Ishaq S, Nunn L. Helicobacter pylori and gastric cancer: A state of the art review. Gastroenterol Hepatol from Bed to Bench. 2015;8: S6–S14. 3. Javaheri A, Kruse T, Moonens K, Mejías-luque R, Debraekeleer A, Asche CI, et al. Helicobacter pylori adhesin HopQ engages in a virulence-enhancing interaction with human CEACAMs. Nat Microbiol. 2016;17: 16189. doi:10.1038/nmicrobiol.2016.189 4. Gray-Owen SD, Blumberg RS. CEACAM1: Contact-dependent control of immunity. Nat Rev Immunol. 2006;6: 433–446. doi:10.1038/nri1864 5. Yang Z. 2007. PAML 4: phylogenetic analysis by maximum likelihood. Mol Biol Evol. 24:1586–1591. 6. Kosakovsky Pond SL, Frost SD. Not so different after all: a comparison of methods for detecting amino acid sites under selection. Molecular biology and evolution. 2005 May 1;22(5):1208-22. 7. Murrell B, Wertheim JO, Moola S, Weighill T, Scheffler K, Pond SL. Detecting individual sites subject to episodic diversifying selection. PLoS genetics. 2012 Jul;8(7). 8. Guindon S, Dufayard JF, Lefort V, Anisimova M, Hordijk W, Gascuel O. New algorithms and methods to estimate maximum-likelihood phylogenies: assessing the performance of PhyML 3.0. Syst