Herpes Simplex Virus 1 US3 Phosphorylates Cellular KIF3A To Downregulate CD1d Expression

Abstract

Herpes simplex virus 1 (HSV-1) causes one of the most prevalent herpesviral infections in humans and is the leading etiological agent of viral encephalitis and eye infections. Our understanding of how HSV-1 interacts with the host at the cellular and organismal levels is still limited. We and others previously reported that, upon infection, HSV-1 rapidly and efficiently downregulates CD1d cell surface expression and suppresses the function of NKT cells, a group of innate T cells with critical immunoregulatory function. The viral protein kinase US3 plays a major role in this immune evasion mechanism, and its kinase activity is required for this function. In this study, we investigated the cellular substrate(s) phosphorylated by US3 and how it mediates US3 suppression of CD1d recycling. We identified the type II kinesin motor protein KIF3A as a critical kinesin factor in the cell surface expression of CD1d. Interestingly, KIF3A is phosphorylated by US3 both in vitro and in infected cells. Mass spectrometry analysis of purified KIF3A showed that it is phosphorylated predominantly at serine 687 by US3. Ablation of this phosphorylation abolished US3-mediated downregulation of CD1d expression, suggesting that phosphorylation of KIF3A is the primary mechanism of HSV-1 suppression of CD1d expression by US3 protein. Understanding of the precise mechanism of viral modulation of CD1d expression will help to develop more efficient vaccines in the future to boost host NKT cell-mediated immune responses against herpesviruses. IMPORTANCEHerpes simplex virus 1 (HSV-1) is among the most common human pathogens. Little is known regarding the exact mechanism by which this virus evades the human immune system, particularly the innate immune system. We previously reported that HSV-1 employs its protein kinase US3 to modulate the expression of the key antigen-presenting molecule CD1d to evade the antiviral function of NKT cells. Here we identified the key cellular motor protein KIF3A as a cellular substrate phosphorylated by US3, and this phosphorylation event mediates US3-induced immune evasion.

A VP22-Null HSV-1 Is Impaired in Inhibiting CD1d-Mediated Antigen Presentation

“…A recent publication indicates that KIF3A, a subunit of kinesin-2 motor protein that transports protein complexes along microtubule tracks, is required for CD1d surface expression (43). KIF3A can be phosphorylated by the viral kinase U S 3 and downregulates CD1d surface expression (43). This is consistent with our discovery that VP22, a viral protein modifies host cell microtubule network, is important in inhibiting CD1d-mediated antigen presentation.…”

“…Nonetheless, gB itself is not sufficient to inhibit CD1d-mediated antigen presentation (35). A recent publication indicates that KIF3A, a subunit of kinesin-2 motor protein that transports protein complexes along microtubule tracks, is required for CD1d surface expression (43). KIF3A can be phosphorylated by the viral kinase U S 3 and downregulates CD1d surface expression (43).…”

Characterization of a Herpes Simplex Virus 1 (HSV-1) Chimera in Which the Us3 Protein Kinase Gene Is Replaced with the HSV-2 Us3 Gene

“…It has been reported that HSV-1 Us3, the best-studied alphaherpesvirus Us3 homologue, blocked apoptosis (16)(17)(18)(19), promoted vesicle-mediated nucleocytoplasmic transport of nucleocapsids through nuclear membranes (20)(21)(22)(23), promoted gene expression by blocking histone deacetylation (24)(25)(26), controlled infected-cell morphology (15,18,27), modulated host immune systems (28)(29)(30)(31)(32)(33)(34)(35), stimulated mRNA translation by activating mTORC1 (36), regulated intracellular trafficking of the abundant virion component UL47 (37) and the essential envelope glycopro-tein B (gB) (38,39), and upregulated the enzymatic activity of viral dUTPase (vdUTPase) (40). These observations suggested that HSV-1 Us3 is a multifunctional protein that regulates various cellular and viral functions by phosphorylating a number of cellular and viral protein substrates.…”

Immune Evasion by Herpes Simplex Viruses

“…Thus, by interfering with complement components HSVs increase their viability in the mucosae and sera of infected patients, which favors the infection of target cells. [175][176][177] gC, gD (glycoprotein C, D); U S 3 (short unique region 3); C3b, C5 (complement component 3b, 5); NK (natural killer cell); CD112 (nectin-2); DNAM-1 (DNAX accessory molecule-1); MICA (MHC class I polypeptide-related sequence A); ULBP1, 2, and 3 (UL16 binding protein 1, 2 and 3); KIF3A (kinesin family member 3); CD1d (antigen-presenting glycoprotein CD1d).…”