Novel role of homogalacturonan region of pectin in disrupting the interaction between fibronectin and integrin β1

Abstract

Pectin interacts with fibronectin (FN), a modular protein in the extracellular matrix. This interaction is significant as FN plays a pivotal role by binding to the receptor integrin α5β1. However, the molecular mechanism underlying the pectin-FN interaction and its impact on integrin binding remains unknown. In this study, water-soluble pectins (WSPs) were extracted from three different pectin sources and subsequently characterized. These included Citrus WSP, which primarily comprises the homogalacturonan region, and Kaki and Yuzu WSPs, both of which are rich in rhamnogalacturonan regions. We investigated the molecular interactions between these WSPs and two FN fragments, Anastellin and RetroNectin, using surface plasmon resonance analysis. Citrus WSP exhibited a notable binding affinity to FN, with a dissociation constant (KD) of approximately 10−7 M. In contrast, Kaki and Yuzu WSPs displayed comparatively weaker or negligible binding affinities. The binding reactivity of Citrus WSP with FN was notably diminished following the enzymatic removal of its methyl-ester groups. Additionally, Citrus WSP disrupted the binding of integrin β1 to RetroNectin without altering the affinity, despite its minimal direct binding to integrin itself. This study furthers our understanding of the intricate pectin-FN interaction and sheds light on their potential physiological relevance and impact on cellular responses.