Sharpe Group

Sharpe Group
Sharpe Group
Hayley Sharpe
Tenure Track Group Leader
Sharpe Group

Research Summary

We are interested in understanding how the cells that make up our tissues and organs communicate. Our cells are decorated with proteins, or receptors, that can sense alterations in their local environment and promote signalling pathways leading to changes in behaviour such as growth, movement or attachment. We focus on receptors that communicate to the cell interior through an enzyme known as a protein phosphatase. These receptor tyrosine phosphatases can change the function of other proteins by catalysing the removal of phosphate groups. The principles of how these receptors contribute to signalling remain poorly understood.
 

The receptor tyrosine phosphatases are linked to diverse areas of biology from immune cell signalling to blood vessel development to cell-cell adhesion, with some implicated in disease processes such as spinal cord injury, wound healing and cancer. Importantly, protein tyrosine phosphatases are targets of reactive oxygen species, which serve as critical signalling molecules that can be dysregulated in ageing and disease. To understand the normal and pathological functions of phosphatases we use biochemistry, proteomics, primary and cancer cell lines, as well as mouse models.
 

 

Latest Publications

Foster WS, Lee JL, Thakur N, Newman J, Spencer AJ, Davies S, Woods D, Godfrey L, Hay IM, Innocentin S, Yam-Puc JC, Horner EC, Sharpe HJ, Thaventhiran JE, Bailey D, Lambe T, Linterman MA Immunology

Emergence from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been facilitated by the rollout of effective vaccines. Successful vaccines generate high-affinity plasma blasts and long-lived protective memory B cells. Here, we show a requirement for T follicular helper (Tfh) cells and the germinal center reaction for optimal serum antibody and memory B cell formation after ChAdOx1 nCoV-19 vaccination. We found that Tfh cells play an important role in expanding antigen-specific B cells while identifying Tfh-cell-dependent and -independent memory B cell subsets. Upon secondary vaccination, germinal center B cells generated during primary immunizations can be recalled as germinal center B cells again. Likewise, primary immunization GC-Tfh cells can be recalled as either Tfh or Th1 cells, highlighting the pluripotent nature of Tfh cell memory. This study demonstrates that ChAdOx1 nCoV-19-induced germinal centers are a critical source of humoral immunity.

+view abstract Cell reports. Medicine, PMID: 36455555 15 Nov 2022

Hay IM, Shamin M, Caroe ER, Mohammed ASA, Svergun DI, Jeffries CM, Graham SC, Sharpe HJ, Deane JE Signalling

The type IIB receptor protein tyrosine phosphatases (R2B RPTPs) are cell surface transmembrane proteins that engage in cell adhesion via their extracellular domains (ECDs) and cell signaling via their cytoplasmic phosphatase domains. The ECDs of R2B RPTPs form stable, homophilic, trans interactions between adjacent cell membranes. Previous work has demonstrated how one family member, PTPRM, forms head-to-tail homodimers. However, as the interface was composed of residues conserved across the family, the determinants of homophilic specificity remain unknown. Here, we have solved the X-ray crystal structure of the membrane-distal, N-terminal domains of PTPRK that form a head-to-tail dimer consistent with intermembrane adhesion. Comparison with the PTPRM structure demonstrates inter-domain conformational differences that may define homophilic specificity. Using small-angle X-ray scattering, we determined the solution structures of the full-length ECDs of PTPRM and PTPRK, identifying that both are rigid, extended molecules that differ in their overall long-range conformation. Furthermore, we identify one residue, W351, within the interaction interface that differs between PTPRM and PTPRK and show that mutation to glycine, the equivalent residue in PTPRM, abolishes PTPRK dimer formation in vitro. This comparison of two members of the receptor tyrosine phosphatase family suggests that homophilic specificity is driven by a combination of shape complementarity and specific but limited sequence differences.

+view abstract The Journal of biological chemistry, PMID: 36436563 24 Nov 2022

Hay IM, Mulholland KE, Lai T, Graham SC, Sharpe HJ, Deane JE Signalling

Protein tyrosine phosphatase receptor-type kappa (PTPRK) is a transmembrane receptor that links extracellular homophilic interactions to intracellular catalytic activity. Previously we showed that PTPRK promotes cell-cell adhesion by selectively dephosphorylating several cell junction regulators including the protein Afadin (Fearnley et al, 2019). Here, we demonstrate that Afadin is recruited for dephosphorylation by directly binding to the PTPRK D2 pseudophosphatase domain. We mapped this interaction to a putative coiled coil (CC) domain in Afadin that is separated by more than 100 amino acids from the substrate pTyr residue. We identify the residues that define PTP specificity, explaining how Afadin is selectively dephosphorylated by PTPRK yet not by the closely related receptor tyrosine phosphatase PTPRM. Our work demonstrates that PTP substrate specificity can be determined by protein-protein interactions distal to the active site. This explains how PTPRK and other PTPs achieve substrate specificity despite a lack of specific sequence context at the substrate pTyr. Furthermore, by demonstrating that these interactions are phosphorylation-independent and mediated via binding to a non-catalytic domain, we highlight how receptor PTPs could function as intracellular scaffolds in addition to catalyzing protein dephosphorylation.

+view abstract eLife, PMID: 36264065 20 10 2022

Group Members

Hayley Sharpe

Tenure Track Group Leader

Roksana Dutkiewicz

PhD Student

Tiffany Lai

PhD Student

Lauren Maggs

PhD Student

Katie Mulholland

Postdoc Research Scientist

Oisharja Rahman

Research Assistant

Katarzyna Wojdyla

Postdoc Research Scientist

Leah Wynn

Visiting Student