Abstract
Cell death processes are progressively inactivated during malignant development, in part by loss of tumor suppressors that can promote cell death. The Bin1 gene encodes a nucleocytosolic adaptor protein with tumor suppressor properties, initially identified through its ability to interact with and inhibit malignant transformation by c-Myc and other oncogenes. Bin1 is frequently missing or functionally inactivated in breast and prostate cancers and in melanoma. In this study, we show that Bin1 engages a caspase-independent cell death process similar to type II apoptosis, characterized by cell shrinkage, substratum detachment, vacuolated cytoplasm, and DNA degradation. Cell death induction was relieved by mutation of the BAR domain, a putative effector domain, or by a missplicing event that occurs in melanoma and inactivates suppressor activity. Cells in all phases of the cell cycle were susceptible to death and p53 and Rb were dispensable. Notably, Bin1 did not activate caspases and the broad spectrum caspase inhibitor ZVAD.fmk did not block cell death. Consistent with the lack of caspase involvement, dying cells lacked nucleosomal DNA cleavage and nuclear lamina degradation. Moreover, neither Bcl-2 or dominant inhibition of the Fas pathway had any effect. In previous work, we showed that Bin1 could not suppress cell transformation by SV40 large T antigen. Consistent with this finding, we observed that T antigen suppressed the death program engaged by Bin1. This observation was interesting in light of emerging evidence that T antigen has roles in cell immortalization and human cell transformation beyond Rb and p53 inactivation. In support of a link to c-Myc-induced death processes, AEBSF, a serine protease inhibitor that inhibits apoptosis by c-Myc, potently suppressed DNA degradation by Bin1. Our findings suggest that the tumor suppressor activity of Bin1 reflects engagement of a unique cell death program. We propose that loss of Bin1 may promote malignancy by blunting death penalties associated with oncogene activation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing
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Amino Acid Chloromethyl Ketones / pharmacology
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Antigens, Polyomavirus Transforming / physiology
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Apoptosis / physiology*
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Bone Neoplasms / genetics
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Bone Neoplasms / metabolism
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Bone Neoplasms / pathology
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Carcinoma, Hepatocellular / genetics
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Carcinoma, Hepatocellular / metabolism
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Carcinoma, Hepatocellular / pathology
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Carrier Proteins / chemistry
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Carrier Proteins / genetics
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Carrier Proteins / physiology*
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Caspases / physiology*
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Cell Adhesion
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Cell Size
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Cell Transformation, Neoplastic / genetics
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Cysteine Proteinase Inhibitors / pharmacology
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DNA Fragmentation
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Enzyme Activation
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Gene Expression Regulation, Neoplastic
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Humans
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Liver Neoplasms / genetics
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Liver Neoplasms / metabolism
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Liver Neoplasms / pathology
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Mitochondria / physiology
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / physiology*
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Osteosarcoma / genetics
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Osteosarcoma / metabolism
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Osteosarcoma / pathology
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Protein Structure, Tertiary
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Proto-Oncogene Proteins c-bcl-2 / physiology
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Proto-Oncogene Proteins c-myc / antagonists & inhibitors*
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Proto-Oncogene Proteins c-myc / metabolism
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Recombinant Fusion Proteins / physiology
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Retinoblastoma Protein / physiology
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Serine Proteinase Inhibitors / pharmacology
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Sulfones / pharmacology
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Tumor Cells, Cultured / metabolism
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Tumor Suppressor Protein p53 / physiology
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Tumor Suppressor Proteins*
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fas Receptor / physiology
Substances
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Adaptor Proteins, Signal Transducing
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Amino Acid Chloromethyl Ketones
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Antigens, Polyomavirus Transforming
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BIN1 protein, human
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Carrier Proteins
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Cysteine Proteinase Inhibitors
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Nuclear Proteins
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Proto-Oncogene Proteins c-bcl-2
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Proto-Oncogene Proteins c-myc
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Recombinant Fusion Proteins
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Retinoblastoma Protein
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Serine Proteinase Inhibitors
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Sulfones
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Tumor Suppressor Protein p53
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Tumor Suppressor Proteins
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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fas Receptor
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4-(2-aminoethyl)benzenesulfonylfluoride
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Caspases