ABSTRACT
The MYC protooncogene is associated with the pathogenesis of most human neoplasia. Conversely, its experimental inactivation elicits oncogene addiction. Besides constituting a formidable therapeutic target, MYC also has an essential function in normal physiology, thus creating the need for context-specific targeting strategies. The analysis of post-translational MYC activity modulation yields novel targets for MYC inactivation. Specifically, following regulatory network analysis in human B-cells, we identify a novel role of the STK38 kinase as a regulator of MYC activity and a candidate target for abrogating tumorigenesis in MYC-addicted lymphoma. We found that STK38 regulates MYC protein stability and turnover in a kinase activity-dependent manner. STK38 kinase inactivation abrogates apoptosis following B-cell receptor activation, whereas its silencing significantly decreases MYC levels and increases apoptosis. Moreover, STK38 knockdown suppresses growth of MYC-addicted tumors in vivo, thus providing a novel viable target for treating these malignancies.
Subject(s)
B-Lymphocytes/metabolism , Lymphoma, B-Cell/metabolism , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Animals , Apoptosis , Carcinogenesis , Cell Line, Tumor , Cell Transformation, Neoplastic/genetics , Gene Expression Regulation, Neoplastic , HEK293 Cells , HeLa Cells , Heterografts , Humans , Mice , Mice, SCID , Neoplasm Transplantation , Protein Processing, Post-Translational , Protein Serine-Threonine Kinases/genetics , RNA Interference , RNA, Small Interfering , Receptors, Antigen, B-Cell/metabolismABSTRACT
Proteins cross-reacting with antibodies directed against alpha- and beta-spectrin were recently detected in plant cells. In this report we have studied the ability of these proteins to interact with other components of membrane skeleton such as ankyrin, f-actin and calmodulin. It was found that the polypeptide of high molecular weight reacting with anti-alpha-spectrin antibody binds calmodulin in Ca(2+)-dependent manner. Protein complexes containing polypeptides cross-reacting with anti-spectrin antibodies interact with muscle f-actin (in co-sedimentation assay) and with erythrocyte ankyrin (ELISA-type assay). These data further substantiate a possibility of occurrence of spectrin-based membrane skeleton in higher plant cells.
Subject(s)
Pisum sativum/chemistry , Plant Proteins/chemistry , Plant Proteins/metabolism , Spectrin/chemistry , Actins/metabolism , Animals , Ankyrins/metabolism , Antibodies , Calmodulin/metabolism , Cross Reactions , Enzyme-Linked Immunosorbent Assay , Erythrocytes/metabolism , Molecular Weight , Muscle, Skeletal/metabolism , Plant Proteins/isolation & purification , Rabbits , Spectrin/isolation & purification , Spectrin/metabolismABSTRACT
It was found either in Western-blot analysis or in indirect immunofluorescence microscopy that cells of the alga Chlamydomonas reinhardtii contain polypeptides cross-reacting with antibodies directed against red blood cell spectrin. The protein could also be detected by immunoprecipitation with anti-spectrin antibodies. C. reinhardtii cells contain distinct polypeptide chains reacting with antibodies directed against either alpha- or beta-spectrin subunits. This protein was extracted from the cells with low ionic strength solution but was not with nonionic detergent.
Subject(s)
Chlamydomonas reinhardtii/chemistry , Spectrin/analysis , Animals , Antibodies , Cattle , Cell Extracts , Cross Reactions , Epitopes/analysis , Fluorescent Antibody Technique, Indirect , Molecular Weight , Precipitin Tests , Proteins/analysis , Proteins/chemistry , Spectrin/immunology , Spectrin/isolation & purificationABSTRACT
It was found either in Western-blot analysis or in indirect immunofluorescence microscopy that cells of the alga Chlamydomonas reinhardhi contain polypeptides cross-reacting with antibodies directed against red blood cell spectrin. The protein could also be detected by immunoprecipitation with anti-spectrin antibodies. C. reinhardtii cells contain distinct polypeptide chains reacting with antibodies directed against either alpha- or beta-spectrin subunits. This protein was extracted from the cells with low ionic strength solution but was not with nonionic detergent.
Subject(s)
Antibodies/immunology , Chlamydomonas reinhardtii/chemistry , Plant Proteins/immunology , Spectrin/immunology , Animals , Antigen-Antibody Reactions , Blotting, Western , Fluorescent Antibody Technique , Peptides/isolation & purification , Plant Proteins/analysis , Precipitin TestsABSTRACT
Proteins that react with anti-human spectrin antibodies raised in rabbit were found in pea seedlings and leaves. The immunoreactive proteins seem to be associated with the membranes and can be extracted with low ionic strength solutions.
