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Updated: Aug 9, 2025
16:01
Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis
Published on: January 26, 2015
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Exploring the consequences of redirecting an exocytic Rab onto endocytic vesicles.
Xia Li1, Dongmei Liu1, Eric Griffis2
1Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States.
Biorxiv : the Preprint Server for Biology
|February 17, 2023
Summary
Cells can tolerate misdirected Rab GTPases, crucial regulators of vesicular transport. This study shows that even when exocytic Rabs are redirected to endocytic vesicles, cellular growth and protein secretion remain largely unaffected.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Bidirectional vesicular traffic is essential for cellular function, connecting exocytic and endocytic pathways.
- Rab GTPases are key regulators, with distinct Rabs marking anterograde and retrograde vesicles to ensure directional transport.
Approach:
- Engineered a fusion protein combining the Sec4 GEF catalytic domain (Sec2) with the CUE domain of Vps9.
- Investigated the localization and function of this construct, which redirects the exocytic Rab Sec4 to endocytic vesicles.
Key Points:
- The engineered construct localized to puncta dependent on ubiquitin binding, recruiting Sec4 and its effectors.
- These puncta contained clusters of vesicles, with dynamic traffic observed via FRAP analysis.
- Cells expressing the construct exhibited near-normal growth and protein secretion despite Rab misdirection.
Conclusions:
- Vesicular transport is remarkably tolerant of Rab misdirection.
- While Rabs are critical, their precise localization may be less stringent than previously thought for basic cellular functions.
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