Enhancement of Cell Adhesion by Anaplasma phagocytophilum Nucleolin-interacting Protein AFAP

Abstract

Anaplasma phagocytophilum, the aetiologic agent of human granulocytic anaplasmosis (HGA) is an obligate intracellular Gram-negative bacterium. During infection, A. phagocytophilum enhances the adhesion of neutrophils to infected endothelial cells. However the bacterial factors contributing to this phenomenon remain unknown. In this study, we characterized a type IV secretion system substrate of A. phagocytophilum, AFAP (an actin filament-associated Anaplasma phagocytophilumprotein), and found it enhanced cell adhesion. Tandem affinity purification combined with mass spectrometry identified host nucleolin as an AFAP-binding protein. Further study showed disruption of nucleolin by RNA interference and treatment of a nucleolin-binding DNA aptamer AS1411 attenuated AFAP-mediated cell adhesion. The characterization of AFAP with enhancement effect on cell adhesion and identification of its interaction partner may help understand the mechanism underlying A. phagocytophilum-promoting cell adhesion, facilitating elucidation of HGA pathogenesis.HighlightsAnaplasma phagocytophilum AFAP localized to cell periphery.AFAP enhanced cell adhesion.AFAP interacted with host nucleolin.Disruption of nucleolin attenuated AFAP-mediated cell adhesion.