The phosphatase Shp2 is required for signaling by the Kaposi's sarcoma-associated herpesvirus viral GPCR in primary endothelial cells

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma (KS), an AIDS-related endothelial cell malignancy that is the most common cancer in central and southern Africa. The KSHV viral G protein-coupled receptor (vGPCR) is a viral oncogene that conveys a survival advantage to endothelial cells and causes KS-like tumors in mouse models. In this study we investigate the role of Shp2, a protein tyrosine phosphatase in vGPCR signaling. Shp2 is vital to many cytokine-induced signaling pathways and is dysregulated in various infections and malignancies. It has also recently been implicated in angiogenesis. We find that vGPCR activity results in phosphorylation of regulatory tyrosines in Shp2 and that in turn, Shp2 is required for vGPCR-mediated activation of MEK, NFκB, and AP-1. Furthermore, both genetic and chemical inhibition of Shp2 abrogate vGPCR-induced enhancement of endothelial cell migration. This establishes Shp2 as an important point of convergence of KSHV vGPCR signaling and a potential molecular target in the design of an anti-KSHV therapeutic regimen.

The Kaposi's Sarcoma-Associated Herpesvirus G Protein-Coupled Receptor Contains an Immunoreceptor Tyrosine-Based Inhibitory Motif That Activates Shp2

“…The scratch assay in Fig. 4C shows that the vGPCR-ITIM mutant is also deficient at stimulating endothelial cell migration, consistent with a role for Shp2 in angiogenesis (3,13). The presence of functional ITIMs in GPCRs has so far received little attention (9,22,24).…”

“…A scratch wound was introduced and medium changed to M199 with 1% fetal bovine serum (FBS). The number of cells migrating into the wound was determined as was wound width at 16 h and 40 h postwounding as described previously (3). Bars, standard deviations; * , P Յ 0.005 (Student's t test).…”

Modulation of oncogenic signaling networks by Kaposi’s sarcoma-associated herpesvirus

“…It is proposed that lytic cells can exhibit a paracrine effect on neighboring cells by secreting inflammatory or angiogenic factors that are highly prevalent in KSHV-associated diseases. For instance, endothelial cells treated with media harvested from viral G protein-coupled receptor (vGPCR)/ORF74 expressing cells had activated extracellular signal-regulated kinases 1/2 (ERK1/2), which is a kinase upregulated in KSHV malignancies (Bakken et al, 2010). …”

The regulatory roles of phosphatases in cancer

“…Constitutive activation of the vGPC receptor, the Kaposi's herpes sarcoma virus associated chemokine has been shown to result in the phosphorylation of SHP2 (267). The vGPCR contains a bona fide immunoreceptor tyrosine-based inhibitory motif (ITIM) that binds and constitutively activates Shp2 (268).…”