Identification of Barkor as a mammalian autophagy-specific factor for Beclin 1 and class III phosphatidylinositol 3-kinase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 49; pp. 19211 - 19216
• Main Authors: Sun, Qiming, Fan, Weiliang, Chen, Keling, Ding, Xiaojun, Chen, She, Zhong, Qing
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.12.2008; National Acad Sciences
• Subjects: Animals; Antibodies; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Autophagy - physiology; Autophagy - radiation effects; Beclin-1; Binding, Competitive; Biological Sciences; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line, Tumor; Cell lines; Cells; Cloning; Drug regulation; Fluorescence; Humans; Kidney - cytology; Kinases; Mammals; Mathematical functions; Membrane Proteins - genetics; Membrane Proteins - metabolism; Osteosarcoma; Pathogens; Phosphatidylinositol 3-Kinases - metabolism; Phosphatidylinositols; Proteins; Salmonella; Salmonella Infections - metabolism; Salmonella typhimurium; Signal Transduction - physiology; Transfection; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; Ultraviolet Rays; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0810452105

Autophagy mediates the cellular response to nutrient deprivation, protein aggregation, and pathogen invasion in human. Dysfunction of autophagy has been implicated in multiple human diseases including cancer. The identification of novel autophagy factors in mammalian cells will provide critical mechanistic insights into how this complicated cellular pathway responds to a broad range of challenges. Here, we report the cloning of an autophagy-specific protein that we called Barkor (Beclin 1-associated autophagy-related key regulator) through direct interaction with Beclin 1 in the human phosphatidylinositol 3-kinase class III complex. Barkor shares 18% sequence identity and 32% sequence similarity with yeast Atg14. Elimination of Barkor expression by RNA interference compromises starvation- and rapamycin-induced LC3 lipidation and autophagosome formation. Overexpression of Barkor leads to autophagy activation and increased number and enlarged volume of autophagosomes. Tellingly, Barkor is also required for suppression of the autophagy-mediated intracellular survival of Salmonella typhimurium in mammalian cells. Mechanistically, Barkor competes with UV radiation resistance associated gene product (UVRAG) for interaction with Beclin 1, and the complex formation of Barkor and Beclin1 is required for their localizations to autophagosomes. Therefore, we define a regulatory signaling pathway mediated by Barkor that positively controls autophagy through Beclin 1 and represents a potential target for drug development in the treatment of human diseases implicated in autophagic dysfunction.