Fig. 6: SAHA and SE486-11 bind directly to USP5.
From: A novel combination therapy targeting ubiquitin-specific protease 5 in MYCN-driven neuroblastoma
a Single agent and combination binding of SAHA and SE486-11 were measured using microscale thermophoresis assay and 20 µM of purified and labelled USP5 protein. When added as a single agent, SAHA (blue circles) interacted with USP5 in a dose-response manner with KD of 2.76 µM. A kinetic curve was unable to be fitted onto the SE486-11 dose-response data (green triangles). When used in combination (red squares), there was a significant increase in affinity to 159 nM. Shown is the mean ± SD of three independent experiments. b Hypothetical binding model of SAHA (pink sticks) and SE486-11 (green sticks) to USP5 (grey ribbon). The putative “activation loop” is shown in grey sticks, with Phe429 highlighted in purple. This residue pi-stacks with SAHA, stabilising its interaction with the zinc ion (purple sphere). A bound ubiquitin molecule is shown as a pink ribbon. c Hypothetic model of the combination drug inhibition and inactivation of USP5 leads to elevated unanchored polyubiquitin levels, reduced MYCN stability, and consequently lower USP5 protein expression.
