A bifunctional protein regulates mitochondrial protein synthesis

Area of Science:

• Mitochondrial biology
• Molecular cell biology
• Biochemistry

Background:

• Mitochondrial gene expression relies on post-transcriptional regulation by RNA-binding proteins.
• The AU-binding homolog of enoyl-coenzyme A (CoA) hydratase (AUH) is a bifunctional protein with known RNA-binding and leucine catabolism roles.
• AUH's mitochondrial function remained uninvestigated despite its mitochondrial targeting sequence.

Purpose of the Study:

• To investigate the role of AUH in mitochondrial function.
• To determine AUH's localization and interaction within mitochondria.
• To elucidate the impact of AUH levels and catalytic activity on mitochondrial gene expression and cellular respiration.

Main Methods:

• Immunofluorescence and cell fractionation to determine AUH localization.
• Co-immunoprecipitation to assess association with mitochondrial ribosomes.
• RNA interference (RNAi) and plasmid overexpression to manipulate AUH levels.
• Analysis of mitochondrial morphology, RNA stability, biogenesis, and respiratory function.
• Assessment of AUH's catalytic activity in relation to mitochondrial regulation.

Main Results:

• AUH localizes to the inner mitochondrial membrane and matrix, associating with mitochondrial ribosomes.
• Altered AUH levels (decrease or overexpression) impair mitochondrial translation.
• Defects in mitochondrial translation lead to altered morphology, reduced RNA stability, impaired biogenesis, and decreased respiratory function.
• AUH's catalytic activity influences mitochondrial translation and biogenesis, particularly in response to leucine availability.

Conclusions:

• AUH is a key regulator of mitochondrial protein synthesis and function.
• AUH's localization and association with mitochondrial ribosomes are critical for its role.
• Both AUH levels and its catalytic activity, especially concerning leucine metabolism, are essential for maintaining mitochondrial health and cellular respiration.