Amino Acid Availability Modulates Vacuolar H+-ATPase Assembly

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The vacuolar H(+)-ATPase (V-ATPase) is a proton pump crucial for cellular processes, regulated by V1 and V0 domain assembly.
• V-ATPase activity is linked to mTORC1 signaling and nutrient sensing via the Ragulator complex.

Purpose of the Study:

• To investigate the role of amino acid availability in V-ATPase assembly and activity.
• To determine if V-ATPase assembly changes are linked to V-ATPase/Ragulator interactions.

Main Methods:

• Cell fractionation was used to measure V-ATPase assembly in HEK293T cells under varying amino acid conditions.
• V-ATPase activity was assessed by measuring proton transport in lysosomes.
• The roles of PI3K, mTORC1, and lysosomal pH were examined.

Main Results:

• V-ATPase assembly significantly increased upon amino acid starvation and was reversed upon amino acid readdition.
• Lysosomes from starved cells showed enhanced V-ATPase-dependent proton transport, indicating increased catalytic activity.
• These amino acid-dependent changes were independent of PI3K and mTORC1 but were blocked by lysosomal neutralization.

Conclusions:

• Amino acid availability directly regulates V-ATPase assembly and activity.
• Lysosomal pH is a critical factor in controlling V-ATPase assembly in response to amino acids.
• This study identifies a novel signaling pathway regulating V-ATPase assembly distinct from PI3K/mTORC1.