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bioRxiv · 10.1101/2020.02.11.943233

Structural insights into secretory immunoglobulin A and its interaction with a pneumococcal adhesin

Wang, Y.·Wang, G.·Li, Y.·Shen, H.·Chu, H.·Gao, N.·Xiao, J.
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Abstract

Secretory Immunoglobulin A (SIgA) is the most abundant antibody at the mucosal surface. SIgA possesses two additional subunits besides IgA: the joining chain (J-chain) and secretory component (SC). SC is the ectodomain of the polymeric immunoglobulin receptor (pIgR), which functions to transport IgA to the mucosa. The underlying mechanism of how the J-chain and pIgR/SC facilitates the assembly and secretion of SIgA remains to be understood. During the infection of Streptococcus pneumoniae, a pneumococcal adhesin SpsA hijacks SIgA and unliganded pIgR/SC to evade host defense and gain entry to human cells. How SpsA specifically targets SIgA and pIgR/SC also remains unclear. Here we report a cryo-electron microscopy structure of the Fc region of human IgA1 (Fc) in complex with J-chain and SC (Fc-J-SC), which reveals the organization principle of SIgA. We also present the structure of Fc-J-SC in complex with SpsA, which uncovers the specific interaction between SpsA and human pIgR/SC. These results advance the molecular understanding of SIgA and shed light on the pathogenesis of S. pneumoniae.

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Wang, Y., Wang, G., Li, Y., Shen, H., Chu, H., Gao, N., Xiao, J.. 2020-02-11. Structural insights into secretory immunoglobulin A and its interaction with a pneumococcal adhesin. https://doi.org/10.1101/2020.02.11.943233

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