Promiscuous Binding at the Crossroads of Numerous Cancer Pathways: Insight from the Binding of Glutaminase Interacting Protein with Glutaminase L

Abstract

The Glutaminase Interacting Protein (GIP) is composed of a single PDZ domain that interacts with a growing list of partner proteins, including Glutaminase L, that are involved in a number of cell signaling and cancer pathways. Therefore, GIP makes a good target for structure-based drug design. Here we report the solution structures of both free GIP and GIP bound to the C-terminal peptide analog of Glutaminase L. This is the first reported NMR structure of GIP in a complex with one of its binding partners. Our analysis of both free GIP and GIP complexed with the Glutaminase L peptide provides important insights into how a promiscuous binding domain can have affinity for multiple binding partners. Through a detailed chemical shift perturbation analysis and backbone dynamics studies, we demonstrate here that the binding of the Glutaminase L peptide to GIP is an allosteric event. Taken together, the insights reported here lay the groundwork for the future development of a specific inhibitor for GIP.

Identification of brain-specific angiogenesis inhibitor 2 as an interaction partner of glutaminase interacting protein

“…The helix content was found to be reduced by ~ 47%, random coil content by ~ 8% and the β-sheet structure content increased by ~ 29%. Although, the increase in β-sheet content in all these cases can be explained by the mode of binding of these peptides to the GIP through β-strand addition, closer examination of the representative complex structure of GIP with its binding partner does not show any change in the helical content but does indicate some displacement of the helical structure in space [7, 9]. …”

“…The binding pocket of PDZ domains and the mode of binding to the interacting partner proteins are each well characterized [4,7,8,9]. The GLGF motif present in the binding pocket of PDZ domains plays a major role in binding interactions with the target protein.…”

“…Peptides representing these C-terminal recognition motifs have been shown to act as surrogates for their corresponding partner proteins in vitro . Several classes of PDZ domains have been reported based on this specificity [4 7–9…”

“…Structurally, GIP is made up of two α-helices and eight β-strands [9]. GIP is also striking for the promiscuity of its binding profile.…”

“…GIP is also striking for the promiscuity of its binding profile. Some of the reported interacting proteins include Glutaminase L, β-Catenin, FAS, HTLV Tax and HPV E6, which are involved in signalling pathways, energy generation pathways or oncogenic processes [1,2,7–9,].…”