Almost all cellular functions involve communication via protein phosphorylation. This process is mediated by enzymes called kinases, which covalently modify their direct target proteins (substrates) on Serine, Threonine or Tyrosine residues with the γ-phosphate from a molecule of ATP. Phosphorylation of a substrate alters its activity by inducing a change in its structure, localization, binding properties or enzyme kinetics. This in turn influences downstream cellular functions, such as cell shape, survival, gene transcription, etc. Therefore, phosphorylation signalling pathways are an important mechanism used by the cell to transmit signals that regulate vital cellular functions.
The Neurosignalling Group focuses on 3 kinases: Cdk5, GSK3 and PCTK2. These are closely-related Ser/Thr protein kinases that are highly or exclusively (for PCTK2) expressed in the brain. Cdk5 and GSK3 have been implicated in the regulation of important brain functions, such as neurite outgrowth, synapse formation, neurotransmission and neuron survival. PCTK2, on the other hand, has been largely neglected and remains to be investigated. Perhaps the best way of understanding the physiological function of a kinase is to identify its substrates, since this is the primary function of any kinase. To do this, the Neurosignalling Group employs a range of techniques, including the KESTREL screen and the BIPPS technique. So far, this approach has discovered several new substrates of Cdk5 and GSK3 in the brain, including one that is hyperphosphorylated in the brains of Alzheimer’s disease patients (called CRMP2). The neurological function of substrate phosphorylation is investigated using custom-generated phospho-specific antibodies, in vitro phosphorylation assays, neuronal cell culture, immunofluorescence microscopy and transgenic models. This research will help us better understand the molecular mechanisms regulating healthy brain function. Importantly, it also addresses signalling defects that arise during aging and in devastating neurodegenerative diseases like Alzheimer’s disease.