The GTPase activating protein Gyp7 regulates Rab7/Ypt7 activity on late endosomes.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Rab GTPases function as organelle identity markers within the endomembrane system.
• Guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) regulate Rab GTPase localization and activity.
• Mechanisms of GEF and GAP organelle targeting and activity regulation remain largely uncharacterized.

Purpose of the Study:

• To investigate the organelle targeting and function of the GTPase activating protein Gyp7 in yeast.
• To elucidate the role of Gyp7 in regulating the Ypt7 GTPase and its impact on vacuole morphology and endolysosomal transport.
• To explore the lipid requirements for Gyp7 membrane binding and activity.

Main Methods:

• Microscopy to observe Gyp7 localization and vacuole morphology.
• Genetic manipulation to induce mistargeting of Gyp7.
• In vitro lipid-binding and activity assays for Gyp7.
• Analysis of endolysosomal transport and TORC1 signaling pathways.

Main Results:

• Gyp7 was surprisingly observed exclusively in puncta near the yeast vacuole.
• Mistargeting Gyp7 to the vacuole impaired vacuole morphology and endolysosomal transport.
• Gyp7 demonstrated specific lipid requirements for membrane binding and GTPase activating protein activity.
• Gyp7 overexpression led to Ypt7 concentration in late endosomes and rapamycin resistance, indicating a role in signaling endosomes.

Conclusions:

• Gyp7's endosomal localization is critical for its function in regulating Ypt7.
• Gyp7 is essential for efficient endolysosomal transport and likely functions in signaling endosomes.
• Gyp7 is proposed to be part of the regulatory machinery governing late endosome function.