Biomaterial Database

Site-specific tyrosine phosphorylation of IkappaBalpha negatively regulates its inducible phosphorylation and degradation. 1996

S Singh, and B G Darnay, and B B Aggarwal

Cytokine Research Laboratory, Department of Molecular Oncology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.

The transcription factor NF-kappaB is retained in the cytoplasm by its interaction with the inhibitory subunit known as IkappaB. Signal-induced serine phosphorylation and subsequent ubiquitination of IkappaBalpha target it for degradation by the 26 S proteasome. Recently, pervanadate, a protein-tyrosine phosphatase inhibitor, was shown to block the degradation of IkappaBalpha, thus inhibiting NF-kappaB activation. We investigated the mechanism by which pervanadate inhibits the degradation of IkappaBalpha. Western blot analysis of IkappaBalpha from tumor necrosis factor-treated cells revealed a slower migrating IkappaBalpha species that was subsequently degraded. However, pervanadate-treated cells also revealed a slower migrating species of IkappaBalpha that appeared in a time- and dose-dependent manner and was not degraded by tumor necrosis factor. The slower migrating species of IkappaBalpha from pervanadate-treated cells was tyrosine-phosphorylated as revealed by cross-reactivity with anti-phosphotyrosine antibodies, by the ability of the specific tyrosine phosphatase PTP1B to dephosphorylate it, and by phosphoamino acid analysis of IkappaBalpha immunoprecipitated from 32P-labeled cells. By site-specific mutagenesis and deletion analysis, we identified Tyr-42 on IkappaBalpha as the phosphoacceptor site. Furthermore, in an in vitro reconstitution system, tyrosine-phosphorylated IkappaBalpha was protected from degradation. Our results demonstrate that inducible phosphorylation and degradation of IkappaBalpha are negatively regulated by phosphorylation at Tyr-42, thus preventing NF-kappaB activation.

UI	MeSH Term	Description	Entries
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010766	Phosphorylation	The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.	Phosphorylations
D004268	DNA-Binding Proteins	Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.	DNA Helix Destabilizing Proteins,DNA-Binding Protein,Single-Stranded DNA Binding Proteins,DNA Binding Protein,DNA Single-Stranded Binding Protein,SS DNA BP,Single-Stranded DNA-Binding Protein,Binding Protein, DNA,DNA Binding Proteins,DNA Single Stranded Binding Protein,DNA-Binding Protein, Single-Stranded,Protein, DNA-Binding,Single Stranded DNA Binding Protein,Single Stranded DNA Binding Proteins
D004790	Enzyme Induction	An increase in the rate of synthesis of an enzyme due to the presence of an inducer which acts to derepress the gene responsible for enzyme synthesis.	Induction, Enzyme
D004791	Enzyme Inhibitors	Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.	Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme
D006367	HeLa Cells	The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for, among other things, VIRUS CULTIVATION and PRECLINICAL DRUG EVALUATION assays.	Cell, HeLa,Cells, HeLa,HeLa Cell
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000072000	NF-KappaB Inhibitor alpha	An I-kappa B protein that inhibits the activity of dimeric NF-KAPPA B P50-REL complexes, sequesters transcription factor NF-kappaB as an inactive complex in the cytoplasm; and prevents NF-kappaB nuclear translocation and DNA binding.	I Kappa B-alpha Protein,IKappaB-alpha,IKappaBalpha,Major Histocompatibility Complex Enhancer-Binding Protein MAD3,p40 Protein (IKappaB-alpha),I Kappa B alpha Protein,IKappaB alpha,Inhibitor alpha, NF-KappaB,Major Histocompatibility Complex Enhancer Binding Protein MAD3,NF KappaB Inhibitor alpha,alpha, NF-KappaB Inhibitor
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships