S-adenosylmethionine metabolism buffering is regulated by a decrease in glycine N-methyltransferase via the nuclear...

Area of Science:

• Metabolic regulation
• Cellular homeostasis
• Biochemistry

Background:

• Metabolic homeostasis relies on balanced metabolite production and consumption.
• Mechanisms controlling metabolite consumption, particularly S-adenosylmethionine (SAM), are under-investigated.
• SAM metabolism is crucial for methylation, polyamine biosynthesis, and transsulfuration.

Purpose of the Study:

• To investigate the regulation of SAM consumption in *Drosophila* fat body (FB) under SAM-limiting conditions.
• To elucidate the role of glycine N-methyltransferase (Gnmt) in maintaining SAM stability.
• To understand the involvement of the nuclear ubiquitin-proteasome system (UPS) in SAM homeostasis.

Main Methods:

• Analysis of SAM levels in *Drosophila* FB during nutrient deprivation.
• Investigating the degradation pathway of Gnmt using the nuclear UPS.
• Employing genetic manipulation to suppress nuclear UPS function and observe effects on starvation tolerance.

Main Results:

• Gnmt, a key SAM-consuming enzyme in the FB, is degraded via the nuclear UPS during starvation.
• Inhibition of SAM synthesis and starvation conditions lead to decreased Gnmt levels.
• Suppression of nuclear UPS-mediated Gnmt reduction enhances starvation tolerance.

Conclusions:

• Nuclear UPS-mediated degradation of Gnmt is a mechanism to maintain SAM levels under conditions of SAM shortage.
• This regulatory pathway plays a significant role in metabolic adaptation to starvation.
• Targeting Gnmt regulation via the nuclear UPS could be a strategy for enhancing stress tolerance.