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Probing condensate microenvironments and functions with a micropeptide “killswitch”

ABSTRACT: Biomolecular condensates are implicated in many cellular processes, and are thought to create subcellular microenvironments that regulate specific biochemical activities 1-7. For example, in vitro experiments suggest that condensates enable non-stochiometric enrichment of small molecules within condensates 8-12. However, probing the microenvironments of condensates in cells is a major challenge, because tools to selectively manipulate specific condensates in living cells are limited. Here we developed a non-natural micropeptide (i.e., the “killswitch”) and a Nanobody-based recruitment system as a universal approach to probe endogenous condensates, and demonstrate direct links between condensate microenvironments and function in cells. The killswitch is a hydrophobic, aromatic-rich sequence with an ability to self-associate, and no homology to human proteins. When recruited to endogenous and disease-specific condensates in human cells, the killswitch arrested the dynamics of the condensate-forming proteins, which led to predicted and unexpected effects. Targeting the killswitch to the nucleolar protein NPM1 altered nucleolar composition, and inhibited the dynamics of a ribosomal protein within nucleoli. Targeting the killswitch to fusion oncoprotein condensates inhibited the dynamics of effector proteins in the condensates, altered condensate composition, and inhibited proliferation of condensate-driven leukemia cells. In adenoviral nuclear condensates, the killswitch inhibited partitioning of capsid protein into condensates, and suppressed viral particle assembly. The results suggest that the microenvironment within cellular condensates has an essential contribution to non-stochiometric enrichment and the dynamics of effector proteins. The killswitch is a widely applicable tool to alter the material properties of endogenous condensates, and as a consequence, to probe functions of condensates linked to diverse physiological and pathological processes in living systems.

ORGANISM(S): Homo sapiens

PROVIDER: GSE284494 | GEO | 2025/04/10

REPOSITORIES: GEO

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Project description:Biomolecular condensates are implicated in many cellular processes, and are thought to create subcellular microenvironments that regulate specific biochemical activities. For example, in vitro experiments suggest that condensates enable non-stoichiometric enrichment of small molecules within condensates. However, probing the microenvironments of condensates in cells is a major challenge, because tools to selectively manipulate specific condensates in living cells are limited. Here we developed a non-natural micropeptide (i.e., the “killswitch”) and a Nanobody-based recruitment system as a universal approach to probe endogenous condensates, and demonstrate direct links between condensate microenvironments and function in cells. The killswitch is a hydrophobic, aromatic-rich sequence with an ability to self-associate, and no homology to human proteins. When recruited to endogenous and disease-specific condensates in human cells, the killswitch arrested the dynamics of the condensate-forming proteins, which led to predicted and unexpected effects. Targeting the killswitch to the nucleolar protein NPM1 altered nucleolar composition, and inhibited the dynamics of a ribosomal protein within nucleoli. Targeting the killswitch to fusion oncoprotein condensates inhibited the dynamics of effector proteins in the condensates, altered condensate composition, and inhibited proliferation of condensate-driven leukemia cells. In adenoviral nuclear condensates, the killswitch inhibited partitioning of capsid protein into condensates, and suppressed viral particle assembly. The results suggest that the microenvironment within cellular condensates has an essential contribution to non-stoichiometric enrichment and the dynamics of effector proteins. The killswitch is a widely applicable tool to alter the material properties of endogenous condensates, and as a consequence, to probe functions of condensates linked to diverse physiological and pathological processes in living systems.

Project description:Like tobacco smoking, habitual marijuana smoking causes numerous adverse pulmonary effects. However, the mechanisms of action involved, especially as compared to tobacco smoke, are still unclear. To uncover putative modes of action, this study employed a toxicogenomics approach to compare the toxicological pathways perturbed following exposure to marijuana and tobacco smoke condensate in vitro. Condensates of mainstream smoke from hand-rolled tobacco and marijuana cigarettes were similarly prepared using identical smoking conditions. Murine lung epithelial cells were exposed to low, medium and high concentrations of the smoke condensates for 6 hr. RNA was extracted immediately or after a 4-hr recovery period and hybridized to mouse whole genome microarrays. Tobacco smoke condensate (TSC) exposure was associated with changes in xenobiotic metabolism, oxidative stress, inflammation, and DNA damage response. These same pathways were also significantly affected following marijuana smoke condensate (MSC) exposure. Although the effects of the condensates were largely similar, dose-response analysis indicates that the MSC is substantially more potent than TSC. In addition, steroid biosynthesis, apoptosis, and inflammation pathways were more significantly affected following MSC exposure, whereas m-phase cell cycle pathways were more significantly affected following TSC exposure. MSC exposure also appeared to elicit more severe oxidative stress than TSC exposure, which may account for the greater cytotoxicity of MSC. This study shows that in general, MSC impacts many of the same molecular processes as TSC. However, subtle pathway differences can provide insight into the differential toxicities of the two complex mixtures. Murine epithelial lung cells were exposed to tobacco smoke condensates (0, 25, 50, 90 Î¼g/ml) or marijuana smoke condensates (0, 2.5, 5, 10 Î¼g/ml) in serum-free medium for a six hour period. Following the six-hour exposure, cells were either harvested immediately or washed with phosphate-buffered saline and incubated in fresh serum-free medium for a four hour recovery period. Total RNA was extracted from the cells and hybridized against Universal Mouse Reference RNA (Agilent Technologies Canada, Inc.) to Agilent whole mouse genome microarray slides containing 44,000 transcripts. A LOWESS normalization was applied to expression results, and statistically significant genes were identified using the R library MAANOVA. Microarray results were validated by real time RT-PCR.

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Probing condensate microenvironments and functions with a micropeptide “killswitch”

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