Falcon deep research report on nhr-49 (C. elegans)
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NHR-49 is a sequence-specific transcription factor of the nuclear receptor
superfamily, functionally comparable to mammalian lipid-sensing nuclear
receptors (PPARalpha by functional analogy, HNF4alpha by structural
similarity), and is among the best-characterized C. elegans NHRs.
"**NHR-49 is a sequence-specific transcription factor of the nuclear receptor superfamily**. It is widely described as functionally comparable to mammalian lipid-sensing nuclear receptors, especially **PPARα** (functional analogy) and **HNF4α** (structural similarity), and is among the best-characterized *C. elegans* NHRs"
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The central mechanistic theme is that NHR-49 coordinates transcriptional
programs balancing lipid catabolism (beta-oxidation), fatty-acid
desaturation, lipid remodeling, and stress-protective responses.
"the central mechanistic theme is that **NHR-49 coordinates transcriptional programs that balance lipid catabolism (β-oxidation), fatty-acid desaturation, lipid remodeling, and stress-protective responses**"
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NHR-49 acts as a transcriptional regulator that can both activate and
repress metabolic gene programs, activating fatty-acid beta-oxidation
targets (acs-2, cpt-5, ech-1) and regulating desaturases (fat-5, fat-6,
fat-7).
"**Primary function**: NHR-49 acts as a **transcriptional regulator** that can both **activate** and **repress** metabolic gene programs.
- It activates gene modules involved in **fatty-acid β-oxidation** (including canonical targets such as **acs-2, cpt-5, ech-1**) and regulates **fatty-acid desaturation** genes (**fat-5, fat-6, fat-7**)"
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NHR-49 regulates distinct gene subsets via context-dependent partnerships
with other NHRs: NHR-80 for fatty-acid desaturase genes and NHR-66 for
sphingolipid/lipid remodeling genes.
"NHR-49 was shown to regulate distinct gene subsets via **partnerships with other NHRs**, notably:
- **NHR-80**: linked to regulation of **fatty-acid desaturase** genes.
- **NHR-66**: linked to regulation of **sphingolipid/lipid remodeling** genes."
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MDT-15 (a Mediator subunit) is a critical co-regulator for NHR-49-driven
transcriptional outputs in metabolism and stress programs.
"Multiple studies converge on **MDT-15 (Mediator subunit)** as a critical co-regulator for NHR-49-driven transcriptional outputs in metabolism and stress programs"
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NHR-49 is an orphan nuclear receptor: its ligand-binding domain is
functionally important and likely ligand-responsive, but no definitive
endogenous ligand has been established, so any ligand should be phrased as
putative.
"Evidence strongly supports that **the LBD is functionally important** and likely ligand-responsive, but **a definitive endogenous ligand for NHR-49 is not established**."
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NHR-49 controls an essential hypoxia survival pathway that operates in
parallel to HIF-1, being required for hypoxia-induced autophagosome
(LGG-1::GFP) formation in seam cells.
"A major mechanistic expansion beyond “lipid metabolism” is an **essential hypoxia survival pathway** controlled by NHR-49 that operates **in parallel to HIF-1**, with NHR-49 being required for hypoxia-induced autophagosome formation (LGG-1::GFP foci) in seam cells"
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NHR-49/MDT-15 couples lipid metabolic remodeling to HSF-1-dependent heat
shock response and proteostasis; intestinal NHR-49 activation improves
proteostasis outcomes (Sala et al. 2024, Genes & Development).
"A 2024 Genes & Development study places NHR-49/MDT-15 as a signaling module that links lipid metabolic remodeling to **HSF-1-dependent heat shock response** and proteostasis"
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A cell-autonomous neuronal role for NHR-49 in oxygen-sensing URX/AQR/PQR
neurons is required for pathogen (PA14) lawn avoidance and normal neuronal
calcium kinetics (Kwon et al. 2024, Cells).
"A 2024 Cells paper identifies a **cell-autonomous neuronal role**: loss of nhr-49 causes impaired pathogen lawn avoidance (PA14) associated with **prolonged URX calcium transients after O2 upshift**, and neuronal rescue in URX/AQR/PQR improves both behavior and calcium kinetics"
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Loss of nhr-49 causes high fat, impaired fasting response, shortened
lifespan, altered mitochondrial morphology/function, defective pathogen
avoidance, and increased sensitivity to oxidative stress, hypoxia, and
infection.
"Loss of **nhr-49** causes high fat, impaired fasting response, shortened lifespan, altered mitochondrial morphology and function, defective pathogen avoidance, and increased sensitivity to oxidative stress, hypoxia, and infection"
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NHR-49 is required for induction of phase II detoxification programs in
oxidative stress contexts and works with MDT-15.
"NHR-49 is required for induction of detoxification programs (phase II enzymes) in oxidative stress contexts and works with MDT-15"