Regulated proteolysis of the IFNaR2 subunit of the interferon-alpha receptor.
The type I interferons (IFNs) bind surface receptors, induce JAK kinases and activate STAT transcription factors to stimulate the transcription of genes downstream of IFN-stimulated response elements (ISREs). In this study, we demonstrate that IFNaR2, a subunit of the type I IFN receptor, is proteolytically cleaved in a regulated manner. Immunoblotting shows that multi-step cleavage occurs in response to phorbol ester (PMA) and IFN-alpha, generating both a transmembrane 'stub' and the intracellular domain (ICD), similar to Notch proteolysis. Isolated membrane fractions process IFNaR2 to release the ICD. A chimeric receptor construct is utilized to show that cleavage requires the presenilins and occurs in response to epidermal growth factor and protein kinase C-delta overexpression, as well as PMA and type I IFNs. Fluorescence microscopy demonstrates that a green fluorescent protein-ICD fusion localizes predominantly to the nucleus. A fusion between the ICD and the Gal4 DNA-binding domain represses transcription, in a histone deacetylase-dependent manner, of a Gal4 upstream activating sequence-regulated reporter, while overexpression of the ICD alone represses transcription of a reporter linked to an ISRE. Proteolytic cleavage events may facilitate receptor turnover or, more likely, function as a mechanism for signaling similar to that employed by Notch and the Alzheimer's precursor protein.
Saleh
Abu Z M
AZ
Department of Pathology, College of Medicine, University of California, Irvine, CA 92697, USA.
Fang
Aaron T
AT
Arch
Allison E
AE
Neupane
Divas
D
El Fiky
Ashraf
A
Krolewski
John J
JJ
D002460:Cell Line; D006801:Humans; D007370:Interferon Type I / Q000276:immunology / Q000494:pharmacology; D007668:Kidney; D008565:Membrane Proteins; D016133:Polymerase Chain Reaction; D021122:Protein Subunits / Q000378:metabolism; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
C508033:IFNAR2 protein, human; D007370:Interferon Type I; D008565:Membrane Proteins; D021122:Protein Subunits; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D053633:Receptor, Interferon alpha-beta; D013755:Tetradecanoylphorbol Acetate