👤 Brett M Frye

Genetic alterations in FGFR2 drive multiple malignancies, most notably intrahepatic cholangiocarcinoma, where they occur in ∼10-15% of patients. While approved pan-FGFR inhibitors provide clinical benefit, their durability is limited by acquired, often polyclonal, on-target resistance mutations affecting key regions of the FGFR2 kinase domain, including the gatekeeper residue (V565), molecular brake residues (N550, E566, K642), and other key variants. These liabilities motivate the development of next-generation inhibitors. Given FGFR2-associated toxicities and the need for subtype selectivity, FGFR4 inhibition was prioritized as a selectivity determinant, while sparing FGFR1 was considered less critical. Guided by structure-based drug design, a reversible aminopyrimidine screening hit was optimized into a novel covalent inhibitor series active against FGFR2 wild-type and clinically relevant resistance mutations. An advanced lead Show less

TF (transcription factor) Prdm16 (positive regulatory domain-containing protein 16) regulates hematopoietic and neuronal stem cell homeostasis, adipose differentiation, and cardiac development. Its role in the circulatory system extends beyond the heart, as Prdm16 loss in arterial endothelial cells (ECs) impairs arterial reperfusion of ischemic mouse limbs due to endothelial dysfunction, and Zebrafish were used to analyze vascular development, arteriovenous endothelial specification, and the emergence of arteriovenous malformations in the absence or presence of Prdm16 or Notch signaling. Lentiviral-mediated Prdm16 overexpression in human endothelial (progenitor) cells was coupled to qRT-PCR (real-time quantitative polymerase chain reaction), Western blot, and transcriptional profiling to document Prdm16's importance for arterial lineage specification. Coimmunoprecipitation in HEK293 (human embryonic kidney 293) cells was performed to assess physical interaction between Prdm16 and the Notch pathway. Existing mouse and human data sets were reanalyzed to evaluate Prdm16 expression in mammalian arteriovenous malformations. Prdm16 actively promotes arterial EC identity while suppressing venous fate. Like in mice, Prdm16 is expressed by arterial ECs early during vascular development in zebrafish, where it synergistically coordinates arterial development together with canonical notch signaling, as their combined loss in zebrafish leads to arteriovenous malformations. PRDM16's arterializing effect on human ECs is dependent on canonical Notch activity, as it is blunted in the presence of canonical Notch inhibitors and potentiated in the presence of delta-like ligand 4. Mechanistically, Prdm16 does not increase the protein levels of the cleaved intracellular domain of Notch receptors (notch intracellular domain) but rather potentiates the effect of the latter via physical and functional interaction. Prdm16 further finetunes Notch signaling and arterial development by complexing with Hey2 (Hes-related family bHLH TF with YRPW motif 2), the basic helix-loop-helix TF acting downstream of canonical Notch during arterial lineage specification and development. Together, our data demonstrate an intricate interplay between Prdm16 and Notch in ECs and indicate that Prdm16 signaling may constitute a novel therapeutic target for arteriovenous malformations. Show less

Western diets and social subordination are associated with increased risk of cardiovascular disease. In this study, we investigated the impact of Western versus Mediterranean diets and social status on atherogenesis and arterial transcriptional profiles in a 30-month randomized study in middle-aged, cynomolgus monkeys ( Show less

The heterochromatin protein 1 (HP1) sub-family of CBX chromodomains are responsible for the recognition of histone H3 lysine 9 tri-methyl (H3K9me3)-marked nucleosomal substrates through binding of the N-terminal chromodomain. These HP1 proteins, namely, CBX1 (HP1β), CBX3 (HP1γ), and CBX5 (HP1α), are commonly associated with regions of pericentric heterochromatin, but recent literature studies suggest that regulation by these proteins is likely more dynamic and includes other loci. Importantly, there are no chemical tools toward HP1 chromodomains to spatiotemporally explore the effects of HP1-mediated processes, underscoring the need for novel HP1 chemical probes. Here, we report the discovery of HP1 targeting peptidomimetic compounds, UNC7047 and UNC7560, and a biotinylated derivative tool compound, UNC7565. These compounds represent an important milestone, as they possess nanomolar affinity for the CBX5 chromodomain by isothermal titration calorimetry (ITC) and bind HP1-containing complexes in cell lysates. These chemical tools provide a starting point for further optimization and the study of CBX5-mediated processes. Show less

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder, with mutations in hundreds of genes contributing to its risk. Herein, we studied lymphoblastoid cell lines (LCLs) from children diagnosed with autistic disorder ( Show less

Polyubiquitination by E2 and E3 enzymes is a predominant mechanism regulating protein function. Some RING E3s, including anaphase-promoting complex/cyclosome (APC), catalyze polyubiquitination by sequential reactions with two different E2s. An initiating E2 ligates ubiquitin to an E3-bound substrate. Another E2 grows a polyubiquitin chain on the ubiquitin-primed substrate through poorly defined mechanisms. Here we show that human APC's RING domain is repurposed for dual functions in polyubiquitination. The canonical RING surface activates an initiating E2-ubiquitin intermediate for substrate modification. However, APC engages and activates its specialized ubiquitin chain-elongating E2 UBE2S in ways that differ from current paradigms. During chain assembly, a distinct APC11 RING surface helps deliver a substrate-linked ubiquitin to accept another ubiquitin from UBE2S. Our data define mechanisms of APC/UBE2S-mediated polyubiquitination, reveal diverse functions of RING E3s and E2s, and provide a framework for understanding distinctive RING E3 features specifying ubiquitin chain elongation. Show less