Identification of Maleimide-Fused Carbazoles as Novel Noncanonical Bone Morphogenetic Protein Synergizers

Abstract

Morphogenic signaling pathways govern embryonic development and tissue homeostasis on the cellular level. Precise control of such signaling events paves the way for innovative therapeutic approaches in the field of regenerative medicine. In line with these notions, bone morphogenic protein (BMP) is a major osteogenic driver and pharmacological stimulation of BMP signaling holds supreme potential for diseases and defects of the skeleton. Efforts to identify small-molecule modalities that activate or potentiate the BMP pathway have primarily been focused on the canonical signaling cascade. Here, we describe the phenotypic identification and development of specific carbazolomaleimides 2 as novel noncanonical BMP synergizers with submicromolar osteogenic cellular potency. The devised chemical tools are characterized to specifically regulate Id gene expression in a SMAD-independent, yet highly BMP-dependent fashion. Mechanistic studies revealed that GSK3 inhibition and increased β-catenin levels are partly responsible for this activity. The utility of the new BMP synergizer profile was further exemplified by showing how the synergistic action of canonical and noncanonical BMP enhancers additively amplifies BMP-dependent osteogenic outputs. Carbazolomaleimide 2b serves as a new and unique pharmacological tool for the modulation and study of the BMP pathway.

Small-Molecule Probes as Pharmacological Tools for the Bone Morphogenetic Protein Signaling Pathway

“…DIPQUO , and Compound 2b are GSK3 inhibitors, thereby activating canonical Wnt signaling (Figure C, Table ). As indicated above, the cooperation between Wnt and BMP in osteogenesis is well established, and thus, the pronounced pro-osteogenic effect of these compounds is not surprising. , Imidazole­quinolinone DIPQUO was discovered from a phenotypic screen in C2C12 cells (47,000 commercial diversity set, ALP readout).…”

“…The latter was identified from the same PDD platform that furnished Chromenone 1 and CGS-15943 . A comparative analysis of different GSK3 inhibitors showed striking phenotypic differences and contrasting dependency on BMP . The underlying mechanisms driving these distinct cell fates were not unraveled but were hypothesized to derive from the differing regulation of non-canonical BMP effectors.…”

“…Therefore, Compound 2b is currently the only SMAD-independent, non-canonical, yet BMP stimuli-dependent synergizer chemotype. The utility of this new synergizer profile was further underlined by demonstrating how non-canonical ( Compound 2b ) and canonical ( Chromenone 1) BMP potentiators additively amplified osteogenic efficacy in a BMP-dependent manner . However, it should be noted that Compound 2b can only be used as a tool for this purpose within a narrow, submicromolar dose range.…”

“…As indicated above, the cooperation between Wnt and BMP in osteogenesis is well established, and thus, the pronounced pro-osteogenic effect of these compounds is not surprising. , Imidazole­quinolinone DIPQUO was discovered from a phenotypic screen in C2C12 cells (47,000 commercial diversity set, ALP readout). Carbazolo­maleimide Compound 2b was designed from a pharmacophore fusion approach of PD407824 and a 3,4-diaryl­maleimide hit cluster . The latter was identified from the same PDD platform that furnished Chromenone 1 and CGS-15943 .…”

“…Carbazolomaleimide Compound 2b was designed from a pharmacophore fusion approach of PD407824 and a 3,4-diarylmaleimide hit cluster. 142 The latter was identified from the same PDD platform that furnished Chromenone 1 and CGS-15943. A comparative analysis of different GSK3 inhibitors showed striking phenotypic differences and contrasting dependency on BMP.…”