From Generalist to Specialist: Evolution of PS2 α-integrins and Implications for Drug Targeting

Integrins are heterodimeric transmembrane receptors that mediate cell-cell and cell- extracellular matrix interactions and play essential roles in development and disease. Within the PS2 -integrin subfamily, four paralogs (IIb, 5, 8, and V) share a conserved RGD-binding motif yet exhibit diverse functional specializations. Integrins have been widely targeted therapeutically for various clinical conditions, though achieving subtype specificity remains a major challenge. Here, we performed an integrative evolutionary analysis of 114 PS2 -integrin sequences across 28 vertebrate species, combining phylogenetic reconstruction, time calibration, ancestral sequence inference, and structural mapping. Our time-calibrated phylogeny indicates that the PS2 lineage originated [~]862 Mya, with diversification of the four paralogs occurring prior to vertebrate radiation. Ancestral state reconstruction reveals that fibronectin and vitronectin binding are ancestral traits, whereas fibrinogen binding and {beta}3 pairing arose independently in the IIb and V lineage. Evolutionary rate analysis shows domain-specific divergence, with the {beta}-propeller acting as a hotspot of evolutionary change, likely driven by combined pressures from ligand binding and {beta}-subunit interaction. These pressures vary across paralogs: IIb exhibits accelerated evolution in ligand-binding regions, while V displays elevated rates in {beta}-subunit interaction domains. Mapping sequence variation onto structural interfaces identifies lineage-specific substitutions underlying functional divergence, including distinct molecular solutions for fibrinogen binding in IIb and V. These findings collectively demonstrate that PS2 -integrins evolved from a generalist ancestor through neofunctionalization and lineage-specific specialization. This work provides an evolutionary framework for identifying subtype-specific functional sites and highlights the potential of evolution-informed strategies to guide the development of more selective integrin-targeting therapeutics.