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Updated: Apr 12, 2026

Ultrastructural Localization of Endogenous LC3 by On-Section Correlative Light-Electron Microscopy
Published on: March 31, 2023
Divergent roles of BECN1 in LC3 lipidation and autophagosomal function
Ruina He1, Jingyu Peng, Pengfei Yuan
1a Biodynamic Optical Imaging Center (BIOPIC); Peking-Tsinghua Center for Life Sciences; State Key Laboratory of Protein and Plant Gene Research; School of Life Sciences; Peking University ; Beijing , China.
Abstract:
BECN1/Beclin 1 is regarded as a critical component in the class III phosphatidylinositol 3-kinase (PtdIns3K) complex to trigger autophagy in mammalian cells. Despite its significant role in a number of cellular and physiological processes, the exact function of BECN1 in autophagy remains controversial. Here we created a BECN1 knockout human cell line using the TALEN technique. Surprisingly, the complete loss of BECN1 had little effect on LC3 (MAP1LC3B/LC3B) lipidation, and LC3B puncta resembling autophagosomes by fluorescence microscopy were still evident albeit significantly smaller than those in the wild-type cells. Electron microscopy (EM) analysis revealed that BECN1 deficiency led to malformed autophagosome-like structures containing multiple layers of membranes under amino acid starvation. We further confirmed that the PtdIns3K complex activity and autophagy flux were disrupted in BECN1(-/-) cells. Our results demonstrate the essential role of BECN1 in the functional formation of autophagosomes, but not in LC3B lipidation.
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