PD-L1 intracellular interactions that necessitate the TSS motif within the cytoplasmic domain

ABSTRACT: Lymphatic endothelial cells (LEC) comprise lymphatic vessels that guide immune cells to lymph nodes (LN) and form the subcapsular sinus and cortical and medullary lymphatic structures of the LN. During an active immune response the lymphatics remodel to accommodate the influx of immune cells from the tissue. In this study we determined that a TSS motif within the cytoplasmic domain of programmed death ligand 1 (PD-L1), expressed by LECs in the LN, participates in lymphatic remodeling during inflammation. Mutation of the TSS motif to AAA in the cytoplasmic domain of PD-L1 does not affect surface expression of PD-L1 but instead causes defects in LN cortical and medullary lymphatic organization following Poly I:C in vivo. Supporting this observation, in vitro treatment of the LEC cell line, SVEC4-10, with the cytokines TNF alpha and IFN alpha significantly impeded SVEC4-10 movement in the presence of the TSS-AAA cytoplasmic mutation. The cellular movement defects coincided with reduced F-actin polymerization, consistent with differences previously found in dendritic cells. Here, in addition to loss of actin polymerization we define STAT3 and Paxillin as important binding partners to PD-L1. STAT3 and Paxillin were previously demonstrated to be important at focal adhesions for cellular motility. We further demonstrate the TSS-AAA motif mutation of PD-L1 reduced the amount of pSTAT3 and Paxillin bound to PD-L1 both before and after exposure to TNF alpha and IFN alpha. Together, these findings highlight PD-L1 as an important component of a membrane complex that is involved in cellular motility which leads to defects in lymphatic organization.

INSTRUMENT(S): Bruker timsTOF Pro

ORGANISM(S): Mus Musculus (ncbitaxon:10090)

SUBMITTER: Beth Tamburini  

PROVIDER: MSV000089579 | MassIVE | Wed Jun 01 06:41:00 BST 2022

REPOSITORIES: MassIVE