The Kirsten rat sarcoma viral oncoprotein homolog (KRAS) is currently a primary focus of oncologists and translational scientists, driven by exciting results with KRAS-targeted therapies for ...non-small cell lung cancer (NSCLC) patients. While KRAS mutations continue to drive high cancer diagnosis and death, researchers have developed unique strategies to target KRAS variations. Having been investigated over the past 40 years and considered “undruggable” due to the lack of pharmacological binding pockets, recent breakthroughs and accelerated FDA approval of the first covalent inhibitors targeting KRAS G12C , have largely sparked further drug development. Small molecule development has targeted the previously identified primary location alterations such as G12, G13, Q61, and expanded to address the emerging secondary mutations and acquired resistance. Of interest, the non-covalent KRAS G12D targeting inhibitor MRTX-1133 has shown promising results in humanized pancreatic cancer mouse models and is seemingly making its way from bench to bedside. While this manuscript was under review a novel class of first covalent inhibitors specific for G12D was published, These so-called malolactones can crosslink both GDP and GTP bound forms of G12D. Inhibition of the latter state suppressed downstream signaling and cancer cell proliferation in vitro and in mouse xenografts. Moreover, a non-covalent pan-KRAS inhibitor, BI-2865, reduced tumor proliferation in cell lines and mouse models. Finally, the next generation of KRAS mutant-specific and pan-RAS tri-complex inhibitors have revolutionized RAS drug discovery. This review will give a structural biology perspective on the current generation of KRAS inhibitors through the lens of emerging secondary mutations and acquired resistance.
Fungal LOV proteins facilitate photoadaptation via blue light regulation of dimer formation. Despite considerable homology of these proteins in closely related fungi, deviations in signaling exist. ...Here we report the crystal structure of ENVOY (ENV1), a homolog of N. crassa VVD in the fungus T. reesei, a model organism for plant cell wall degradation. Structural studies contradict a model of reversible competitive dimerization. Rather, evolutionary pressures have facilitated a two-residue shift in the position of a key Cys residue (Cys96) that enables the integration of environmental stress and light responses. A Cys96Thr variant abolishes adaptive responses to light and oxidative stress in a carbon source-dependent manner in vivo. Phylogenetic analysis verifies an evolutionary relevance of the Cys residue shift in different orders within Sordariomycetes. In this manner, we identified a widespread oxidative stress signaling mechanism that couples metabolic sensing and blue light responses not previously identified in LOV proteins.
•LOV domains integrate blue-light, carbon sensing and oxidative stress•Competitive models of LOV dimerization are not conserved in all species•Evolutionary pressures select for a two-residue shift, enabling signal integration
LOV proteins regulate adaptive responses in diverse organisms and are widely used in optogenetics. Lokhandwala et al. demonstrate that evolutionary pressures select for a widespread two-residue shift in a key motif to enable LOV domains to integrate light, oxidative stress, and metabolism.
Light-oxygen-voltage (LOV) domain-containing proteins function as small light-activated modules capable of imparting blue light control of biological processes. Their small modular nature has made ...them model proteins for allosteric signal transduction and optogenetic devices. Despite intense research, key aspects of their signal transduction mechanisms and photochemistry remain poorly understood. In particular, ordered water has been identified as a possible key mediator of photocycle kinetics, despite the lack of ordered water in the LOV active site. Herein, we use recent crystal structures of a fungal LOV protein ENVOY to interrogate the role of Thr101 in recruiting water to the flavin active site where it can function as an intrinsic base to accelerate photocycle kinetics. Kinetic and molecular dynamic simulations confirm a role in solvent recruitment to the active site and identify structural changes that correlate with solvent recruitment. In vivo analysis of T101I indicates a direct role of the Thr101 position in mediating adaptation to osmotic stress, thereby verifying biological relevance of ordered water in LOV signaling. The combined studies identify position 101 as a mediator of both allostery and photocycle catalysis that can impact organism physiology.
Key message
FKF1 dimerization is crucial for proper
FT
levels to fine-tune flowering time. Attenuating FKF1 homodimerization increased CO abundance by enhancing its COP1 binding, thereby accelerating ...flowering under long days.
In Arabidopsis (
Arabidopsis thaliana
), the blue-light photoreceptor FKF1 (FLAVIN-BINDING, KELCH REPEAT, F-BOX 1) plays a key role in inducing the expression of
FLOWERING LOCUS T
(
FT
), encoding the main florigenic signal in plants, in the late afternoon under long-day conditions (LDs) by forming dimers with
FT
regulators. Although structural studies have unveiled a variant of FKF1 (FKF1 I160R) that disrupts homodimer formation in vitro, the mechanism by which disrupted FKF1 homodimer formation regulates flowering time remains elusive. In this study, we determined that the attenuation of FKF1 homodimer formation enhances
FT
expression in the evening by promoting the increased stability of CONSTANS (CO), a primary activator of
FT
, in the afternoon, thereby contributing to early flowering. In contrast to wild-type FKF1, introducing the FKF1 I160R variant into the
fkf1
mutant led to increased
FT
expression under LDs. In addition, the FKF1 I160R variant exhibited diminished dimerization with FKF1, while its interaction with GIGANTEA (GI), a modulator of FKF1 function, was enhanced under LDs. Furthermore, the FKF1 I160R variant increased the level of CO in the afternoon under LDs by enhancing its binding to COP1, an E3 ubiquitin ligase responsible for CO degradation. These findings suggest that the regulation of FKF1 homodimerization and heterodimerization allows plants to finely adjust
FT
expression levels around dusk by modulating its interactions with GI and COP1.
Characterization of a Vivid Homolog in Botrytis cinerea Foley, Brandon J.; Stutts, Haley; Schmitt, Sydney L. ...
Photochemistry and photobiology,
September/October 2018, 2018-09-00, 20180901, Letnik:
94, Številka:
5
Journal Article
Recenzirano
Blue light‐signaling pathways regulated by members of the light–oxygen–voltage (LOV) domain family integrate stress responses, circadian rhythms and pathogenesis in fungi. The canonical signaling ...mechanism involves two LOV‐containing proteins that maintain homology to Neurospora crassa Vivid (NcVVD) and White Collar 1 (NcWC1). These proteins engage in homo‐ and heterodimerization events that modulate gene transcription in response to light. Here, we clone and characterize the VVD homolog in Botrytis cinerea (BcVVD). BcVVD retains divergent photocycle kinetics and is incapable of LOV mediated homodimerization, indicating modification of the classical hetero/homodimerization mechanism of photoadaptation in fungi.
Botrytis cinerea Vivid demonstrates divergent photochemical and signaling pathways that differentiate the protein from homologs in Neurospora crassa and Trichoderma reesei. These alterations to signaling mechanisms imply a deviation from the typical homo‐ and heterodimerization models of Vivid signaling.
PDF
