Regulation of neuronal cell adhesion by a DHHC5/Golga7b palmitoyl-acyltransferase complex.

Palmitoylation (S-acylation), the only known reversible lipid modification of proteins, is an important regulator of protein localisation and function. It is involved in many cellular processes, including protein trafficking, stability and signalling and is therefore crucial for all cell types and organisms from yeast to humans. Palmitoylation is mediated by a family of 23 enzymes (protein acyltransferases (PATs)) in humans. Many of these enzymes have been shown to regulate important aspects of cell biology and, in particular, in neuronal cells where palmitoylation of receptors and associated proteins regulate synaptic plasticity and therefore functions such as learning and memory. Indeed, mutations in several of these enzymes are implicated in the pathophysiology of neurological disorders, including a plasma membrane localised synaptic PAT, DHHC5, which is a schizophrenia risk gene.

Recently, we uncovered a novel and central role for DHHC5 in the regulation of cell-cell adhesion in epithelial cells. In this project, the student will investigate the role of DHHC5 in the regulation of synaptic palmitoylation and trans-synaptic adhesion. This project will use proteomic approaches that we are developing to identify synaptic substrates of DHHC5 and investigate how palmitoylation of selected substrates regulates their stability, trafficking and function. We recently identified Golga7b as a critical regulator of DHHC5 localisation and function. The mechanistic basis of this interaction is not understood, and how the large unstructured C-terminus fold upon binding of Golga7b and/or substrates is unknown. A structural mass spectrometry approach could yield important insights into both DHHC5/golga7b complex formation and substrate recognition.

This interdisciplinary project will utilise a range of experimental approaches, including cell culture, molecular and cell biology, chemical biology, protein biochemistry and state-of-the-art quantitative mass spectrometry. The student will be given in-depth training in all of these methods and will benefit from collaborations with other groups within the School of Biosciences and across the faculty.

The aims of the project include the following.

1) Use cross-linking mass spectrometry approaches to characterise the interactions between DHHC5 and Golga7b

2) Develop and apply proteomic approaches to characterise substrates of DHHC5 in CRISPR knockout cell lines

3) Determine how DHHC5/Golg7b regulate neuronal cell adhesion