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Published on: March 26, 2014
KIBRA controls exosome secretion via inhibiting the proteasomal degradation of Rab27a
Lin Song1, Shi Tang1, Xiaolei Han1
1Department of Neurology, Shandong Provincial Hospital affiliated to Shandong University, 250021, Jinan, Shandong, China.
Abstract:
Exosomes are nanosized membrane vesicles released from cells after fusion of multivesicular bodies (MVBs) with the plasma membrane (PM) and play important roles in intercellular communication and numerous biological processes. However, the molecular mechanisms regulating exosome secretion remain poorly understood. Here we identify KIBRA as an adaptor-like protein that stabilizes Rab27a, which in turn controls exosome secretion both in vitro and in vivo. Knockdown or overexpression of KIBRA in neuronal and podocyte cell lines leads to a decrease or increase of exosome secretion, respectively, and KIBRA depletion increases MVB size and number. Comparing protein profiles between KIBRA knockout and wild-type mouse brain showed significantly decreased Rab27a, a small GTPase that regulates MVB-PM docking. Rab27a is stabilized by interacting with KIBRA, which prevents ubiquitination and degradation via the ubiquitin-proteasome pathway. In conclusion, we show that KIBRA controls exosome secretion via inhibiting the proteasomal degradation of Rab27a.
Insights
KIBRA protein stabilizes Rab27a, a key molecule controlling exosome secretion. This discovery reveals a new mechanism regulating how cells communicate via extracellular vesicles.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Exosomes are vital for intercellular communication, but the mechanisms governing their release are not fully understood.
- Multivesicular bodies (MVBs) fuse with the plasma membrane (PM) to release exosomes, a process crucial for biological functions.
Purpose of the Study:
- To identify novel molecular regulators of exosome secretion.
- To elucidate the role of KIBRA in the pathway controlling exosome release.
Main Methods:
- Investigated KIBRA's function in neuronal and podocyte cell lines using knockdown and overexpression.
- Analyzed protein profiles in KIBRA knockout and wild-type mouse brains.
- Examined the interaction between KIBRA and Rab27a, including ubiquitination and degradation pathways.
Main Results:
- KIBRA acts as an adaptor protein that stabilizes Rab27a, a small GTPase essential for exosome secretion.
- KIBRA depletion reduces exosome secretion, increases MVB size and number, and decreases Rab27a levels.
- KIBRA prevents Rab27a ubiquitination and subsequent degradation by the ubiquitin-proteasome system.
Conclusions:
- KIBRA is a critical regulator of exosome secretion by stabilizing Rab27a.
- This study uncovers a novel pathway where KIBRA inhibits Rab27a proteasomal degradation, thereby controlling exosome release.
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