AP-3 and the V-ATPase Modulate CTP Synthase Assembly Through Spatial Association at the Yeast Vacuole

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Metabolic enzymes can form membraneless filaments called cytoophidia for regulation.
• CTP synthase forms pH-sensitive cytoophidia.
• Nutritional stress in yeast affects CTP synthase cytoophidia and vacuolar H+-ATPase (V-ATPase).

Purpose of the Study:

• To investigate the functional link between CTP synthase cytoophidia assembly and V-ATPase disassembly during nutritional deprivation in yeast.
• To explore the role of the AP-3 adaptor complex in regulating Ura7 (yeast CTP synthase homolog) cytoophidia dynamics.

Main Methods:

• Yeast genetics and microscopy to observe Ura7 localization and cytoophidia formation.
• Genetic disruption of the AP-3 adaptor complex.
• Combined nutritional and pharmacological V-ATPase inhibition.

Main Results:

• Ura7 localizes to vacuoles under nutrient-rich and starvation conditions.
• AP-3 disruption alters Ura7 assembly dynamics, reducing structures but enhancing elongation.
• V-ATPase inhibition triggers massive Ura7 cytoophidia formation.

Conclusions:

• A spatial coupling exists between metabolic enzyme compartmentalization (CTP synthase cytoophidia), vacuolar trafficking (AP-3), and pH regulation (V-ATPase).
• CTP synthase assembly dynamics are responsive to vacuolar function, suggesting a novel organizational principle.