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Selective modulation of nuclear receptor LRH-1 through target-ing buried and surface regions of the binding pocket

ABSTRACT: Liver receptor homolog-1 (LRH-1) is a phospholipid-sensing nuclear receptor that has shown promise as a target for alleviat-ing intestinal inflammation and disease states characterized by metabolic dysregulation in the liver. LRH-1 contains an unu-sually large ligand binding pocket, and generating synthetic modulators has been challenging. Leveraging a hexahydropen-talene (6HP) core, we have had recent success in generating potent and efficacious agonists through two distinct strategies. We targeted residues deep within the pocket to enhance compound binding, while residues at the mouth of the pocket were targeted to mimic interactions made by endogenous phospholipids. Here, we unite these two designs into one hybrid mole-cule that is the most potent LRH-1 agonist to date. Through a combination of global transcriptomic, biochemical, and struc-tural studies, we show that selective modulation can be driven through contacting deep vs. surface polar regions in the pock-et. While deep pocket contacts convey high-affinity, contacts with the pocket mouth dominate allostery and provide a phos-pholipid-like transcriptional response in cultured cells.

INSTRUMENT(S): Q Exactive HF, Q Exactive

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Valentine Courouble

LAB HEAD: Patrick Griffin

PROVIDER: PXD031099 | Pride | 2022-05-04

REPOSITORIES: Pride

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			Action	DRS
	12bpLRH1FL_10CA_10_1.raw	Raw
	12bpLRH1FL_10CA_10_2.raw	Raw
	12bpLRH1FL_10CA_10_3.raw	Raw
	12bpLRH1FL_10CA_300_1.raw	Raw
	12bpLRH1FL_10CA_300_2.raw	Raw

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Project description:To directly observe the conformational changes in Akt1 3P elicited by PIP 3 binding, we performed HDX-MS analysis of Akt1 3P in the presence of plasma membrane-mimicking liposomes (20% cholesterol, 30% phosphatidylcholine, 15% phosphatidylserine, 35% phosphatidylethanolamine) that contained either 0% or 5% PIP 3 . The sequence coverage of Akt1 was excellent, with 160 peptides spanning ~97% of all exchangeable amides (Supplementary Table 2). With 5% PIP 3 liposomes there was extensive protection of the PH domain, similar to what had been previously observed for non-phosphorylated Akt1. In addition to protection of the PH domain elicited by PIP 3 binding, Akt1 3P exhibited significant deprotection of the C-lobe of the kinase domain, including the activation loop, that corresponds to the interface between the PH and kinase domains observed in our structure of autoinhibited Akt1. We also carriedout HDX-MS experiments in the presence and absence of ATPS, for which we observed no significant differences. The likely binding pocket for the hydrophobic motif is the so-called PDK1- interacting fragment (PIF) pocket in Akt that binds the phosphorylated hydrophobic motif in the active conformation (21, 22) . Previous hydrogen- deuterium exchange mass spectrometry (HDX-MS) analysis of Akt1 DrLink indicated small, but significant exposure of the PIF pocket upon PI(3,4,5)P 3 binding (26) (Figure 5D, deuterium incorporation plots reproduced with permission). We confirmed this observation by comparing the deuterium incorporation rates for Akt1 DrLink and Akt1 ΔC in solution. Sequence coverage of the truncated Akt1 ΔC comprised 85 peptides spanning ~94% of all exchangeable amides (Supplementary Table 2). Two peptides in Akt1 ΔC , corresponding to β3-αB in the N-lobe and the catalytic loop in the C-lobe of the kinase domain exhibited a modest, but significant, 6% increase in deuterium incorporation (Figure 5E). These changes indicate exposure of the PIF pocket and consequent local disordering of the N-lobe in the absence of the hydrophobic motif. These observationsis areis consistent with the lack of electron density observed for theC helix and activation loop and overall higher temperature factors for the N- lobe of the kinase domain (Supplementary Figure S5CD). In order to test whether the unphosphorylated hydrophobic motif indeed binds to the PIF pocket in the inactive conformation, we measured the binding affinity of a tail peptide 19 containing the missing C-terminal tail residues in Akt1 ΔC (residues 457-480 of human Akt1) by fluorescence anisotropy. The binding constant was estimated to be approximately 0.5 mM from three independent titrations (Figure 5F), although it was not possible to reach saturation due to limiting Akt1 ΔC concentration. Whilst this is a relatively weak interaction, it is sufficient in the context of an intramolecular interaction to sequester the hydrophobic motif more than 99% of the time at equilibrium due to the almost infinite local concentration.

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Selective modulation of nuclear receptor LRH-1 through target-ing buried and surface regions of the binding pocket

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