Tlr3 interacts with ESCRT-I components Tsg101 and Hcrp1 in mouse astrocyte cell line

Abstract

Abstract It is established now that ESCRT (endosomal sorting complex required for transport) complexes participate in the trafficking of endosomal Toll-like receptors (TLRs), which are relevant in the regulation of the TLR-mediated immune response. TLR3 plays a vital role in the innate immune control of herpes simplex type 1 virus (HSV-1) infection in the brain, however, the process of TLR3 delivery to the ligand recognition site and fate as endosomal cargo including the receptor degradation await explication. Proximity ligation assays in TLR3 agonist, poly(I:C) stimulated or unstimulated murine astrocytes, confirmed the association of Tlr3 with Tsg101 and Hcrp1, ESCRT-I subunits essential for the lysosomal sorting of ubiquitinated membrane receptors. The interaction of Tlr3 and ESCRT-I components was prominent in the first hour and 24 h after poly(I:C) addition. TLR3 was highly ubiquitinated in cells at all studied times, while the interaction of Hrs, a core component of ESCRT-0 and ESCRT-I, and Tlr3, as well as Hrs and Tsg101, and Hrs and Hcrp1, increased in the first hour of stimulation, but 24 h following stimulation returned to levels observed in unstimulated cells. Results suggest a possible role of ESCRT-I in prolongation of TLR3 signaling and/or receptor degradation, prompting investigation whether Tsg101 and Hcrp1 influence Tlr3 transportation in cells of the central nervous system, which would portray ESCRT-I as a possible modulation target regarding TLR3-mediated antiviral response in the brain.