The evolutionarily conserved domain of Beclin 1 is required for Vps34 binding, autophagy and tumor suppressor function.

Abstract

Atg6/Beclin 1 is an evolutionarily conserved protein family that has been shown to function in vacuolar protein sorting (VPS) in yeast; in autophagy in yeast, Drosophila, Dictyostelium, C.elegans, and mammals; and in tumor suppression in mice. Atg6/Beclin 1 is thought to function as a VPS and autophagy protein as part of a complex with Class III phosphatidylinositol 3'-kinase (PI3K)/Vps34. However, nothing is known about which domains of Atg6/Beclin 1 are required for its functional activity and binding to Vps34. We hypothesized that the most highly conserved region of human Beclin 1 spanning from amino acids 244-337 is essential for Vps34 binding, autophagy, and tumor suppressor function. To investigate this hypothesis, we evaluated the effects of wild-type and mutant beclin 1 gene transfer in autophagy-deficient MCF7 human breast carcinoma cells. We found that, unlike wild-type Beclin 1, a Beclin 1 mutant lacking aa 244-337 (Beclin 1DeltaECD), is unable to enhance starvation-induced autophagy in low Beclin 1-expressing MCF7 human breast carcinoma cells. In contrast to wild-type Beclin 1, mutant Beclin 1DeltaECD is unable to immunoprecipitate Vps34, has no Beclin 1-associated Vps34 kinase activity, and lacks tumor suppressor function in an MCF7 scid mouse xenograft tumor model. The maturation of cathepsin D, which requires intact Vps34-dependent VPS function, is comparable in autophagy-deficient low-Beclin 1 expressing MCF7 cells, autophagy-deficient MCF7 cells transfected with Beclin 1DeltaECD, and autophagy-competent MCF7 cells transfected with wild-type Beclin 1. These findings identify an evolutionarily conserved domain of Beclin 1 that is essential for Vps34 interaction, autophagy function, and tumor suppressor function. Furthermore, they suggest a connection between Beclin 1-associated Class III PI3K/Vps34-dependent autophagy, but not VPS, function and the mechanism of Beclin 1 tumor suppressor action in human breast cancer cells.

• Authors: Norihiko Furuya, Jie Yu, Maya Byfield, Sophie Pattingre, Beth Levine
• Journal: Autophagy (Autophagy) Vol. 1 Issue 1 Pg. 46-52 (Apr 2005) ISSN: 1554-8627 [Print] United States
• PMID: 16874027 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Apoptosis Regulatory Proteins
• Atg6 protein, Drosophila
• BECN1 protein, human
• Beclin-1
• Drosophila Proteins
• Membrane Proteins
• Vesicular Transport Proteins
• Phosphatidylinositol 3-Kinases
• Cathepsin D

Topics

• Amino Acid Sequence
• Apoptosis Regulatory Proteins (genetics, physiology)
• Autophagy (physiology)
• Beclin-1
• Cathepsin D (metabolism)
• Cell Line, Tumor
• Conserved Sequence
• Drosophila Proteins (genetics, physiology)
• Evolution, Molecular
• Genes, Tumor Suppressor
• Humans
• Membrane Proteins (genetics, physiology)
• Molecular Sequence Data
• Mutation
• Neoplasm Transplantation
• Phosphatidylinositol 3-Kinases (genetics, physiology)
• Protein Binding
• Protein Structure, Tertiary
• Sequence Homology, Amino Acid
• Transplantation, Heterologous
• Vesicular Transport Proteins (genetics, physiology)