Identification and Mechanistic Characterization of a Novel Peptide Inhibitor of Glycogen Synthase Kinase (GSK3) Derived from the Disrupted in Schizophrenia 1 (DISC1) Protein

Glycogen Synthase Kinase 3-beta (GSK3{beta}) is a critical regulator of several cellular pathways involved in neuroplasticity and is a potential target for neurotherapeutic development in the treatment of neuropsychiatric and neurodegenerative diseases. The majority of efforts to develop inhibitors of GSK3{beta} have been focused on developing small molecule inhibitors that compete with ATP through direct interaction with the ATP binding site. This strategy has presented selectivity challenges due to the evolutionary conservation of this domain within the kinome. The Disrupted in Schizophrenia (DISC1) protein, has previously been shown to bind and inhibit GSK3{beta} activity. Here, we report the characterization of a 44-mer peptide derived from human DISC1 (hDISCtide) that is sufficient to both bind and inhibit GSK3{beta} in a non-competitive mode that is distinct from classical ATP competitive inhibitors. Based on multiple independent biochemical and biophysical assays, we propose that hDISCtide interacts at two distinct regions of GSK3{beta}: an inhibitory region that partially overlaps with the binding site of FRATide, a well-known GSK3{beta} binding peptide, and a specific binding region that is unique to hDISCtide. Taken together, our findings present a novel avenue for developing a peptide-based selective inhibitor of GSK3{beta}.