Matthew Call-Projects

Matthew Call-Projects


T cell receptor structure and function

The T cell antigen receptor  (TCR) recognizes peptide fragments bound to major histocompatibility complex (MHC) proteins, activating T cells to kill target cells and/or secrete soluble factors. While the structural determinants of ligand discrimination are well studied, the mechanism by which receptor engagement outside the cell is sensed by signalling molecules inside the cell is still an open question. We are combining disulphide mapping and solution NMR techniques to determine how the eight-subunit receptor complex is arranged within the membrane and how transmembrane structure and dynamics relate to receptor activation. 

Team member: Logesvaran Krshnan

Regulation of cell-surface immune-regulatory proteins by MARCH-family e3 ubiquitin ligases

The levels of peptide:MHC complexes and other immunologically relevant proteins available at the cell surface can be modulated by regulatory proteins of the Membrane-Associated RING-CH (MARCH) family. MARCHs are integral membrane proteins with alpha-helical TM domains and cytosolic ubiquitin ligase domains. We use cellular biochemical and flow-cytometry based functional assays combined with solution NMR and lipidic cubic phase (LCP) crystallography techniques to study how MARCH proteins trap substrates through interactions with their TM domains. The major aim of this project is to identify what structural motifs govern substrate identification and thereby identify new substrates and molecular pathways that are MARCH-regulated.

Team members: Cyrus Tan and Raphael Trenker

Tuning CAR T-cell potency with de novo designed receptor transmembrane domains

With collaborator Sarel Fleishman (Weizmann Institute of Science, Israel), we have developed and validated a panel of de novo designed transmembrane domains (TMDs) that form stable and specific dimeric, trimeric and tetrameric structures in cell membranes. We used these to enforce the corresponding oligomeric states in second-generation chimeric antigen receptors (CARs) against the solid tumour antigen HER2 and showed that both tumour control and cytokine production scaled in direct proportion to the designed oligomeric structure of the TMD (see eLife 2022).

Ongoing work in this program is focused on (1) expanding our panel of available TMD sequences and structures, (2) testing the clinical relevance of these new tools for optimising the safety/efficacy profiles of cellular immunotherapies in specific cancer contexts and (3) developing even more sophisticated applications for these sequences in the CAR T-cell space.

Project resources

Team members:

Melissa Call, Laboratory Head, BSc MSc PhD Auckland

Samyuktha Ramesh, Postdoctoral Fellow, BTech Anna Univ Chennai PhD Melbourne

Ashleigh Davey, Senior Postdoctoral Fellow, BBiotech(Hons) Monash PhD Melbourne

Jasmine Rou, Honours Student, BSc Melbourne

Julie Nguyen, Research Assistant, BSc(Hons) Monash

Margareta Go, Research Assistant, BMedSci Univ Applied Sciences Utrecht

Lincoln Smith, Research Assistant, BBiotech(Hons) PhD Newcastle