Explore the vast range of titles available.

Cotransins target the Sec61 translocon and inhibit the biogenesis of an undefined subset of secretory and membrane proteins. Remarkably, cotransin inhibition depends on the unique signal peptide (SP) of each Sec61 client, which is required for cotranslational translocation into the endoplasmic reticulum. It remains unknown how an SP’s amino acid sequence and biophysical properties confer sensitivity to structurally distinct cotransins. Here we describe a fluorescence-based, pooled-cell screening platform to interrogate nearly all human SPs in parallel. We profiled two cotransins with distinct effects on cancer cells and discovered a small subset of SPs, including the oncoprotein human epidermal growth factor receptor 3 (HER3), with increased sensitivity to the more selective cotransin, KZR-9873. By comparing divergent mouse and human orthologs, we unveiled a position-dependent effect of arginine on SP sensitivity. Our multiplexed profiling platform reveals how cotransins can exploit subtle sequence differences to achieve SP discrimination. Wenzell et al. developed a massively parallel screening platform to interrogate the sensitivity of signal peptides (SPs) to Sec61 inhibitors. The platform revealed how distinct inhibitors achieve sequence-dependent SP discrimination.

Zetomipzomib (KZR-616) is a selective inhibitor of the immunoproteasome currently undergoing clinical investigation in autoimmune disorders. Here, we characterized KZR-616 in vitro and in vivo using multiplexed cytokine analysis, lymphocyte activation and differentiation, and differential gene expression analysis. KZR-616 blocked production of >30 pro-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs), polarization of T helper (Th) cells, and formation of plasmablasts. In the NZB/W F1 mouse model of lupus nephritis (LN), KZR-616 treatment resulted in complete resolution of proteinuria that was maintained at least 8 weeks after the cessation of dosing and was mediated in part by alterations in T and B cell activation, including reduced numbers of short and long-lived plasma cells. Gene expression analysis of human PBMCs and tissues from diseased mice revealed a consistent and broad response focused on inhibition of T, B, and plasma cell function and the Type I interferon pathway and promotion of hematopoietic cell lineages and tissue remodeling. In healthy volunteers, KZR-616 administration resulted in selective inhibition of the immunoproteasome and blockade of cytokine production following ex vivo stimulation. These data support the ongoing development of KZR-616 in autoimmune disorders such as systemic lupus erythematosus (SLE)/LN.

BackgroundMany tumor cells escape immune cell clearance by overexpressing CD47, a multi-pass transmembrane protein, which binds signal regulatory protein α (SIRPα) on macrophages leading to decreased phagocytic activity. Blockade of CD47/SIRPα interactions enhances macrophage phagocytosis and is being targeted with antibody-based drugs, some of which are used in combination therapies in clinical trials. A novel method to target CD47 is through the inhibition of cotranslational translocation of transmembrane proteins. Immediately after exiting the ribosome, signal sequences that are unique to each protein are directed through the Sec61 channel into the ER for extracellular expression.1 Several Sec61-targeting compounds have been identified to suppress translocation in a signal sequence-specific manner.2 We previously described Sec61 inhibitors capable of selectively targeting immune checkpoint proteins and enhancing T cell function.3 Here, we demonstrate the blockade of CD47 expression on tumor cells and enhancement of macrophage phagocytosis with small molecule inhibitors of Sec61.MethodsSec61-dependent expression of target proteins was assayed using HEK293 cells overexpressing constructs comprised of signal sequences fused to a luciferase reporter. Stimulated PBMCs or tumor cells were incubated with Sec61 inhibitors, and surface expression of checkpoint molecules were examined by flow cytometry. Necrotic and apoptotic cells were assessed by Annexin V and 7AAD labeling. Human CD14+ monocytes were differentiated to M1- or M2-type macrophages. Jurkat or SKBR3 cells were incubated with Sec61 inhibitors, labeled with a pH sensitive dye and co-cultured with macrophages to assess phagocytosis.ResultsWe identified Sec61 inhibitors that block select immune checkpoint proteins. Compounds demonstrated either selective or multi-target profiles in transient transfection screens, which was supported by decreased protein expression on activated T cells. KZR-9275 targeted multiple checkpoint molecules, including PD-1, LAG-3 and CD73, along with a potent inhibition of the CD47 signal sequence reporter. CD47 surface expression was decreased on Jurkat and SKBR3 cells following 72 hours of compound treatment. KZR-9275 treatment of SKBR3 cells induced a minor increase in apoptotic cells, which was not detected in Jurkat cells. Increased macrophage phagocytosis, especially with M2-type macrophages, was observed when Jurkat or SKBR3 cells were pre-treated with KZR-9275.ConclusionsOur findings demonstrate that Sec61 inhibitors can block the expression of CD47, a phagocytosis checkpoint protein, on tumor cells and subsequently modulate macrophage phagocytic activity. Small molecule inhibitors of Sec61 provide an opportunity to target multiple checkpoint proteins on various cell populations. Future in vivo tumor models will assess the efficacy of Sec61 inhibitors to provide combination-like therapy.ReferencesPark E, Rapoport TA. Mechanisms of Sec61/SecY-mediated protein translocation across membranes. Annu Rev Biophys 2012; 41:1–20.Van Puyenbroeck V, Vermeire K. Inhibitors of protein translocation across membranes of the secretory pathway: novel antimicrobial and anticancer agents. Cell Mol Life Sci 2018; 75:1541–1558.Whang J, Anderl J, Fan A, Kirk C, Lowe E, McMinn D, et al. Targeting multiple immune checkpoint proteins with novel small molecule inhibitors of Sec61-dependent cotranslational translocation. 34th Annual Meeting & Pre-Conference Programs of the Society for Immunotherapy of Cancer (SITC 2019): part 2. J Immunother Cancer 2019; 7: 283. Abstract 815.

Preventing the biogenesis of disease-relevant proteins is an attractive therapeutic strategy, but attempts to target essential protein biogenesis factors have been hampered by excessive toxicity. Here we describe KZR-8445, a cyclic depsipeptide that targets the Sec61 translocon and selectively disrupts secretory and membrane protein biogenesis in a signal peptide-dependent manner. KZR-8445 potently inhibits the secretion of pro-inflammatory cytokines in primary immune cells and is highly efficacious in a mouse model of rheumatoid arthritis. A cryogenic electron microscopy structure reveals that KZR-8445 occupies the fully opened Se61 lateral gate and blocks access to the lumenal plug domain. KZR-8445 binding stabilizes the lateral gate helices in a manner that traps select signal peptides in the Sec61 channel and prevents their movement into the lipid bilayer. Our results establish a framework for the structure-guided discovery of novel therapeutics that selectively modulate Sec61-mediated protein biogenesis. A selective inhibitor of Sec61 blocks protein entry into the secretory pathway and has therapeutic efficacy in rheumatoid arthritis. A cryo-EM structure of the inhibited Sec61 provides a model for client-selective protein translocation inhibition.

Preventing the biogenesis of disease-relevant proteins is an attractive therapeutic strategy, but attempts to target essential protein biogenesis factors have been hampered by excessive toxicity. Here, we describe KZR-8445, a cyclic depsipeptide that targets the Sec61 translocon and selectively disrupts secretory and membrane protein biogenesis in a signal peptide-dependent manner. KZR-8445 potently inhibits the secretion of proinflammatory cytokines in primary immune cells and is highly efficacious in a mouse model of rheumatoid arthritis. A cryo-EM structure reveals that KZR-8445 occupies the fully opened Se61 lateral gate and blocks access to the lumenal plug domain. KZR-8445 binding stabilizes the lateral gate helices in a manner that traps select signal peptides in the Sec61 channel and prevents their movement into the lipid bilayer. Our results establish a framework for the structure-guided discovery of novel therapeutics that selectively modulate Sec61-mediated protein biogenesis.

Photolabile solid phase support 1 was synthesized and applied for the orthogonal generation of 3′-alkylamine containing oligonucleotides. Protected oligonucleotides cleaved from 1 were used to develop solution phase methods for oligonucleotide modification resulting in 3′-urea and amide linked constructs. Conjugation of a variety of substrates to photogenerated oligonucleotides proceeds rapidly in very high yields and requires relatively few equivalents of reagent. In addition, this method has proven useful for the convergent coupling of biopolymers and may assist in the generation of libraries of oligonucleotides and nucleopeptides in the future. Solid support 2 was used for photolytic generation of oligonucleotides containing 3′-phosphates. The stability of this support to alkaline conditions allows for automated synthesis and deprotection of support bound oligonucleotides to yield solid phase photolabile hybridization probes. These probes may be released from the support under non-denaturing conditions (photolysis). Hybridization probes exhibit high, 1 base mismatch selectivity of 12-nucleotide long targets. These probes are unique in that their photolytic nature enables the release of the affinity bound substrate in a duplexed form. Bioconjugation methods developed with orthogonally generated 3 ′-alkylamine containing oligonucleotides have been applied to the synthesis of nucleopeptide conjugates designed for self-assembly. Such systems will enable alternative approaches for the study of protein-DNA interactions. The recognition helix of the lambda repressor protein, helix 3, was conjugated to DNA containing the lambda operator binding site (197). It was anticipated that, upon hybridization of 197 to its complement, assembly of the recognition peptide into its α-helix would occur. Circular dichroism detected no recognizable α-helix structure upon duplex formation, indicating that the higher effective molarity induced by covalently linking helix 3 to its recognition site was insufficient to effect self-assembly.