Molecular Features Underlying Shp1/Shp2 Discrimination by Immune Checkpoint Receptors

Abstract

Numerous inhibitory immunoreceptors operate by recruiting phosphatase effectors Shp1 and Shp2 through conserved motifs ITIM and ITSM. Despite the similarity, these receptors exhibit distinct effector binding specificities, as exemplified by PD-1 and BTLA, which preferentially recruit Shp2 and Shp1 respectively. The molecular basis of Shp1/Shp2 discrimination is unclear. Here, we provide evidence that optimal PD-1 and BTLA binding to both Shp1 and Shp2 occurs via a bivalent, parallel mode that involves both SH2 domains of Shp1/Shp2. Moreover, PD-1 mainly uses its ITSM to discriminate Shp2 from Shp1 via their C-terminal SH2 domains. Supportive of this model, swapping the Shp1-cSH2 with Shp2-cSH2 enabled PD-1:Shp1 association in T cells. In contrast, BTLA primarily utilizes its ITIM to discriminate Shp1 from Shp2 via their N-terminal SH2 domains. Substitution of glycine at pY+1 position of the PD-1-ITIM with alanine, a residue conserved in several Shp1-recruiting receptors, was sufficient to induce PD-1:Shp1 interaction in T cells. Finally, mutagenesis screening shows that Shp1 recruitment exhibits a bell-shaped dependence on the side chain volume of the pY+1 residue of ITIM. Collectively, we provide a molecular interpretation of the Shp1/Shp2-binding specificities of PD-1 and BTLA, with general implications for the mechanism of effector discrimination by inhibitory receptors.

Mechanistic convergence of the TIGIT and PD-1 inhibitory pathways necessitates co-blockade to optimize anti-tumor CD8+ T cell responses

“…Fiji was used to quantify the fluorescent intensities of TIGIT or PD-1 in CD226 microclusters (Schindelin et al, 2012). Mask images identifying the area of CD226 microclusters were generated by applying the ''subtract background'' command to CD226 (mGFP) images using the default setting (Xu et al, 2021). The fluorescent signals of CD226 (mGFP), TIGIT (mCherry), or PD-1 (mApple) in the masked overlaid images were measured, and used to calculate the CD226 FI/TIGIT FI or CD226 FI/PD-1 FI ratio for each cell.…”

Study on the allosteric activation mechanism of SHP2 via elastic network models and neural relational inference molecular dynamics simulation

“…In addition, SHP1 and SHP2 both contain two contiguous SH2 domains. 52,53 Using sequence alignment and phylogenetic tree methods, Andersen et al compared and analyzed the evolution relationships among vertebrate PTKs, and confirmed that the sequence of SHP2 is closest to the homologous protein SHP1 with a similarity of 60%. 54 As shown in Fig.…”