ECHS1 Human

What is ECHS1 and what is its primary function in human metabolism?

ECHS1 (short-chain enoyl-CoA hydratase) is a multifunctional mitochondrial matrix enzyme primarily responsible for catalyzing the hydration of short-chain enoyl-CoAs in the mitochondrial β-oxidation pathway of fatty acids . Beyond fatty acid oxidation (FAO), ECHS1 also demonstrates enzymatic activity in the degradation of branched-chain amino acids, particularly valine, leucine, and isoleucine . The enzyme was first observed in cow hearts and livers, and human ECHS1 cDNA clones were initially isolated in 1993 . The protein is encoded by the ECHS1 gene mapped to human chromosome 10q26.2–q26.3, which contains eight exons including 5′ and 3′ untranslated regions .

How is ECHS1 transported to the mitochondria?

The ECHS1 precursor protein undergoes a specific transport mechanism to reach the mitochondrial matrix. Initially, it recognizes and binds to the import receptor Tom20 of the translocase of the outer membrane of mitochondria (TOM) complex. This interaction is facilitated by the arylhydrocarbon receptor-interacting protein (AIP). Subsequently, the protein is translocated into the mitochondrial matrix via the channel protein Tom40 . This precise import mechanism ensures that ECHS1 reaches its functional location to participate in FAO and amino acid metabolism within the mitochondrial environment.

What are the typical methods for measuring ECHS1 activity in laboratory settings?

Methodological approaches for measuring ECHS1 activity typically include:

What are the clinical and biochemical features of ECHS1 deficiency?

ECHS1 deficiency is characterized by a spectrum of clinical manifestations and biochemical abnormalities:
Clinical Features:

• Infantile-onset severe developmental delay

• Neurological regression

• Seizures

• Leigh syndrome (LS) or Leigh-like mitochondrial encephalopathy

• Deafness

• Optic nerve atrophy

• Cardiomyopathy

• Poor feeding

• Respiratory insufficiency
  Biochemical Features:

• Elevated plasma lactate

• Increased urine excretion of erythro-2,3-dihydroxy-2-methylbutyrate

• Elevated 3-methylglutaconate (3-MGC) in urine

• Increased methacrylyl-CoA and acryloyl-CoA related metabolites

• Normal acylcarnitine profile

• Brain MRI abnormalities consistent with Leigh syndrome
  The severity spectrum varies considerably, ranging from fatal neonatal presentations to survival into adulthood .

How do mutations in ECHS1 lead to metabolic dysfunction and Leigh syndrome?

ECHS1 deficiency affects metabolism through multiple pathways that contribute to the development of Leigh syndrome:

• Fatty acid oxidation impairment: Reduced ECHS1 activity decreases ATP production by inhibiting FAO, increasing susceptibility to organ dysfunction, particularly in tissues with high energy demands .

• Toxic metabolite accumulation: Blockage of branched-chain amino acid metabolism leads to accumulation of toxic substrates, especially methacrylate-CoAs and acrylate-CoAs .

• Secondary enzyme dysfunction: These toxic metabolites disrupt pyruvate dehydrogenase complexes and electron transport chains, further compromising mitochondrial energy production .

• Mitochondrial dysfunction: The combined effect leads to mitochondrial failure, which particularly affects the central nervous system, causing the neuropathological features of Leigh syndrome .
  These pathophysiological mechanisms explain why patients present with a clinical picture typical of mitochondrial disorders with hyperlactatemia, cardiomyopathy, and encephalopathy .

What genetic variants of ECHS1 have been identified in patients with ECHS1 deficiency?

Several pathogenic variants have been identified in the ECHS1 gene:

How is ECHS1 expression altered in different cancer types?

ECHS1 shows varied expression patterns across different cancer types:

What mechanisms underlie ECHS1's role in cancer progression?

ECHS1 influences cancer progression through multiple mechanisms:

• Fatty acid metabolism reprogramming: ECHS1 can alter cancer cell energy production by regulating fatty acid β-oxidation, affecting cellular bioenergetics .

• Apoptosis regulation:

  • Knockdown of ECHS1 in SW480 cells promotes mitochondrial reactive oxygen species production and decreases mitochondrial membrane potential, inducing apoptosis .

  • ECHS1 is a binding protein for the apoptosis suppressor STAT3, repressing its transcriptional activity, phosphorylation, and the expression of downstream targets like BCL2 .

• Sphingolipid metabolism: In colorectal cancer, ECHS1 enables altered ceramide metabolism by increasing glycosphingolipid synthesis through promotion of UDP-glucose ceramide glycosyltransferase .

• PI3K/Akt/mTOR signaling: ECHS1 mediates activation of this pathway in diverse cancers, suggesting a role in cell survival and proliferation .

• Drug resistance: ECHS1 is involved in doxorubicin resistance in HCC and oxaliplatin/5-fluorouracil resistance in colorectal cancer .

What experimental approaches are used to investigate ECHS1's function in cancer cells?

Researchers employ several methodologies to study ECHS1 in cancer:

• Gene or protein expression profiling: To identify differential expression in cancer tissues versus normal tissues .

• RNA interference techniques: Knockdown of ECHS1 in cancer cell lines to assess effects on:

  • Cell proliferation and viability

  • Apoptosis rates

  • Mitochondrial function

  • Reactive oxygen species production

• Co-immunoprecipitation assays: To identify protein-protein interactions, such as the interaction between ECHS1 and LASP1 in colorectal cancer .

• Dual-luciferase reporter assay: To investigate transcriptional regulation mechanisms, such as ECHS1's interaction with STAT3 .

• Metabolic profiling: To examine alterations in fatty acid oxidation, sphingolipid metabolism, and other metabolic pathways affected by ECHS1 expression changes .

• Drug sensitivity assays: To assess the role of ECHS1 in chemotherapy resistance mechanisms .

How does ECHS1 contribute to ceramide glycosylation and what are the implications for cancer therapy?

ECHS1 plays a significant role in sphingolipid metabolism, particularly in the process of ceramide glycosylation:

• Mechanism: ECHS1 promotes UDP-glucose ceramide glycosyltransferase activity, which converts ceramides (Cer) to glycosphingolipids (HexCer) . In colorectal cancer cells, ECHS1 has been found to interact with LASP1 (LIM and SH3 domain protein 1), and this interaction appears to be crucial for sphingolipid metabolism imbalance .

• Metabolic impact: This conversion reduces the pool of pro-apoptotic ceramides in cancer cells, thereby inhibiting apoptosis and promoting cancer cell survival .

• Therapeutic implications:

  • Inhibition of ECHS1 could potentially restore ceramide levels by blocking ceramide glycosylation, promoting apoptosis in cancer cells .

  • Targeting ECHS1 might sensitize cancer cells to chemotherapeutic agents that act through ceramide-mediated apoptosis pathways .

  • Small molecule inhibitors of ECHS1 have shown promising anticancer effects in preclinical studies .

• Research findings: Knockdown of ECHS1 in SW480 colorectal cancer cells was shown to inhibit ceramide glycosylation, increase ceramide levels, and induce apoptosis through mitochondrial damage mechanisms .

What are the limitations of current ECHS1 research methodologies and how might they be overcome?

Current ECHS1 research faces several methodological challenges:

• Model system limitations:

  • Patient-derived fibroblasts may not fully recapitulate tissue-specific effects of ECHS1 deficiency, particularly in brain and heart tissues most affected in Leigh syndrome.

  • Solution: Development of tissue-specific organoids or iPSC-derived neuronal and cardiac models could provide more relevant disease models .

• Metabolite measurement challenges:

  • Detection of short-lived toxic intermediates like methacrylyl-CoA is technically challenging.

  • Solution: Advanced metabolomics approaches with improved sensitivity and metabolite stabilization techniques are needed .

• Functional redundancy:

  • Other enzymes may partially compensate for ECHS1 deficiency, complicating interpretation of knockdown studies.

  • Solution: CRISPR-based complete knockout studies combined with rescue experiments could better define ECHS1-specific functions.

• Context-dependent effects:

  • ECHS1 shows opposing effects in different cancer types, suggesting context-dependent functions.

  • Solution: Systematic profiling across multiple cancer types with matched normal tissues could help identify cancer-specific regulatory mechanisms .

• Integration with other metabolic pathways:

  • ECHS1 functions at the intersection of multiple metabolic pathways, making it difficult to isolate specific effects.

  • Solution: Systems biology approaches integrating transcriptomics, proteomics, and metabolomics data could provide a more comprehensive view of ECHS1's role in cellular metabolism .

What potential exists for ECHS1-targeted therapeutics in cancer and metabolic disorders?

The therapeutic potential of targeting ECHS1 spans both cancer treatment and metabolic disorder management:
For Cancer Treatment:

• Small molecule inhibitors: Compounds like 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) enhance pro-apoptotic effects on breast cancer cells by suppressing ECHS1 expression .

• Metabolic reprogramming agents: Remoldin has been shown to reverse fatty acid metabolism reprogramming and lipid accumulation in colorectal and breast cancer by downregulating ECHS1, inhibiting fatty acid prolongation and FAO in mitochondria .

• Combination therapies: ECHS1 mediates activation of PI3K/Akt/mTOR signaling pathways in various cancers, suggesting that combining ECHS1 inhibitors with mTOR inhibitors may produce synergistic anticancer effects .

• Overcoming drug resistance: Given ECHS1's involvement in resistance to chemotherapeutic agents like doxorubicin in HCC and oxaliplatin/5-fluorouracil in colorectal cancer, targeting ECHS1 might help overcome chemotherapy resistance .
  For Metabolic Disorders:

• Substrate reduction therapy: Reducing the intake of precursor metabolites (particularly valine) that lead to toxic intermediate accumulation in ECHS1 deficiency.

• Antioxidant therapies: To mitigate oxidative stress resulting from mitochondrial dysfunction in ECHS1 deficiency .

• Enzyme replacement or gene therapy: While currently theoretical, delivering functional ECHS1 enzyme or correcting genetic defects could address the root cause of ECHS1 deficiency.

• Early diagnostic markers: The identification of specific biomarkers like erythro-2,3-dihydroxy-2-methylbutyrate and 3-methylglutaconate in urine organic acid analysis could enable earlier diagnosis and intervention for ECHS1 deficiency .

What are the best experimental models for studying ECHS1 function?

Researchers employ various experimental models to study ECHS1, each with specific advantages:
Cellular Models:

How can researchers effectively differentiate between ECHS1 deficiency and other mitochondrial disorders with similar presentations?

Distinguishing ECHS1 deficiency from other mitochondrial disorders requires a multi-faceted diagnostic approach:

What are the challenges in correlating in vitro ECHS1 studies with in vivo disease manifestations?

Several challenges exist when attempting to translate in vitro findings about ECHS1 to in vivo disease contexts:

• Tissue specificity: ECHS1 deficiency affects tissues with high energy demands (brain, heart) most severely, but most in vitro studies use fibroblasts or cancer cell lines that may have different metabolic requirements and compensatory mechanisms .

• Developmental aspects: The timing of ECHS1 dysfunction during development may critically impact disease manifestation, which is difficult to model in vitro .

• Environmental factors: In vitro systems typically use standardized nutrient media that don't replicate the variable metabolic conditions experienced in vivo, including fasting, dietary changes, and stress conditions.

• Multi-organ interactions: ECHS1 deficiency affects multiple organ systems, and the complex interactions between these systems cannot be adequately modeled in isolated cell cultures.

• Metabolite accumulation dynamics: The build-up of toxic metabolites like methacrylyl-CoA may occur differently in closed in vitro systems compared to in vivo conditions where clearance mechanisms exist .

• Long-term effects: Many in vitro studies are short-term, while the clinical manifestations of ECHS1 deficiency develop over months to years.

• Individual genetic background: Patient-specific genetic modifiers may influence disease severity and presentation, which is difficult to account for in standardized in vitro models . Researchers are addressing these challenges through the development of more sophisticated models such as 3D organoids, co-culture systems, and animal models that better recapitulate the complex in vivo environment.