Evolution of biophysical tools for quantitative protein interactions and drug discovery

Tuning TCR complex recruitment to the T cell antigen coupler (TAC) enhances TAC-T cell function

The T cell antigen coupler (TAC) receptor is a novel synthetic receptor designed to maximize the therapeutic potential of T cells in the absence of tonic signaling or receptor-related toxicities. Prior studies indicated that TACs provide safe and long-lasting anti-tumor immunity in multiple preclinical models of solid tumors supported by mounting clinical evidence. TAC receptors function by targeting a cancer associated surface antigen while recapitulating natural T cell receptor (TCR) signaling, which involves both TCR/CD3 recruitment and intracellular CD4 co-receptor activity. While other receptor designs exist that redirect TCR signaling towards cancer associated antigens, the TAC technology is unique in that antigen binding is distinctly separated from TCR/CD3 complex recruitment. In the present study, we show that single amino-acid changes in the TAC domain responsible for TCR recruitment of a Claudin 18.2-directed TAC receptor led to enhanced in vivo functionality. Analyzing biophysical properties of the receptor suggests that TAC receptors with high TCR affinities are suboptimal compared to receptor constructs that show lower TCR affinities with notably fast off-rates. This work demonstrates that balancing TCR recruitment is critical when designing effective TAC T cell receptors, a concept that may apply more broadly to other therapeutic approaches relying on TCR signaling.

A druggable pocket on PSMD10Gankyrin that can accommodate an interface peptide and doxorubicin

BACKGROUND

PSMD10Gankyrin, a proteasomal chaperone is also an oncoprotein. Overexpression of PSMD10Gankyrin is associated with poor prognosis and survival in many cancers. Therefore, PSMD10Gankyrin is a sought-after drug target in many hard-to-treat cancers. However, its surface appears flat and undruggable. Here, we build on our earlier discovery of a common hot spot region that defined the interface of multiple interacting partners of PSMD10Gankyrin to expose vulnerable spots for a peptide and a small molecule inhibitor.

METHODS

High throughput virtual screening was used to screen compounds against PSMD10Gankyrin. Interaction of PSMD10Gankyrin with the drug or protein (CLIC1) or peptide was studied using any one or more of these techniques; Microscale Thermophoresis, limited trypsinolysis, SPR and ITC. Cytotoxic effect of doxorubicin was evaluated using MTT assay.

RESULTS

We identified doxorubicin as the first-generation small molecule inhibitor of PSMD10Gankyrin. K116 and to a lesser extent R41 on PSMD10Gankyrin contribute to the bulk of binding energy for the peptide EEVD, CLIC1 and doxorubicin. We further demonstrate that PSMD10Gankyrin is an intended target for doxorubicin in cells.

GENERAL SIGNIFICANCE

Drug design against protein interactions in general and PSMD10Gankyrin in particular, remains a challenge. We provide consolidated biophysical evidence for the use of a shared interface motif EEVD as a possible inhibitor of interaction network in cancers driven by PSMD10Gankyrin. We identify a chemical scaffold for designing novel inhibitors of PSMD10Gankyrin. These findings will impact the field of protein interactions in the context of disease biology/drug discovery.