Serendipitous alkylation of a Plk1 ligand uncovers a new binding channel

Abstract

In the current work, unanticipated synthetic byproducts were obtained arising from alkylation of the δ1 nitrogen (N3) of the histidine imidazole ring of the polo-like kinase-1 (Plk1) polo-box domain (PBD)-binding peptide PLHSpT. For the highest affinity byproduct, bearing a C6H5(CH2)8– group, a Plk1 PBD co-crystal structure revealed a new binding channel that had previously been occluded. An N-terminal PEGylated version of this peptide containing a hydrolytically-stable phosphothreonyl residue (pT) bound to the Plk1 PBD with affinity equal to the non-PEGylated parent, yet it exhibited significantly less interaction with the PBDs of the two closely-related Plk2 or Plk3. Treatment of cultured cells with this PEGylated peptide resulted in Plk1 delocalization from centrosomes and kinetochores, and chromosome misalignment that effectively induced mitotic block and apoptotic cell death. This work provides new insights that may advance efforts to develop Plk1 PBD-binding inhibitors as potential Plk1-specific anticancer therapeutic agents.

Enhanced cellular uptake of a TAT-conjugated peptide inhibitor targeting the polo-box domain of polo-like kinase 1

“…The polo-like kinase (Plk) family, which includes four human serine/threonine protein kinases (Plk1, Plk2, Plk3, and Plk4), was shown to be an important family of proteins in cell cycle regulation, cell division, and even proliferation (Liu et al 2011;Barr et al 2004;Dai 2005). For instance, Plk1 is known to play key roles in the regulation of mitotic progression, spindle formation, chromosome segregation, and cytokinesis (Lansing et al 2007; Barr et al 2004).…”

Using Ligand‐Mapping Simulations to Design a Ligand Selectively Targeting a Cryptic Surface Pocket of Polo‐Like Kinase 1

“…[10,11] Recently, a secondary hydrophobic binding site (Figure 1 b) proximal to the primary phosphopeptide binding site has been identified by two independent approaches. [12,13] Crystal structures have revealed that this pocket can accommodate hydrophobic side-chains of several ligands in slightly different binding modes, with a resulting increase in affinity; [12][13][14][15][16] however, when ligands are not bound to it, the pocket is closed. This cryptic pocket therefore presents a classic problem in SBDD targeting a flexible protein surface.…”

“…[12] We thus increased the sampling of relevant ligand-binding conformations by incorporating benzene molecules into the simulations, due to the pockets known affinity for a phenyl moiety. [12,13] Although hydrophilic molecules have previously been used for this purpose at high (2.7 m) concentrations, [27] a lower concentration of 0.2 m was needed in this work to avoid phase separation of benzene and water. Note that an alternative method, site-identification by ligand competitive saturation (SILCS), [28][29][30] uses high concentrations of hydrophobic ligands (1m) in conjunction with an inter-ligand repulsive interaction energy term.…”

The condensin component NCAPG2 regulates microtubule–kinetochore attachment through recruitment of Polo-like kinase 1 to kinetochores

“…In addition, our structure provides another opportunity for developing PLK1 inhibitors that target the PBD. Many extensive studies have been established to develop PLK1 inhibitors that target the PBD [49][50][51] . These studies were initiated from structural investigations of the PBD and PBIP peptide structures 37 .…”