mRNA mutations of type I protein kinase A regulatory subunit alpha in T lymphocytes of a subject with systemic lupus erythematosus.
Systemic lupus erythematosus (SLE) is an autoimmune disorder of indeterminate etiology characterized by multiple T lymphocyte immune effector dysfunctions. Protein kinase A (PKA) isozymes contribute to the regulation of T cell immune effector functions. In SLE T cells, there is a profound deficiency of PKA-I isozyme activity characterized by both reduced RI alpha transcript and RI alpha protein levels. To identify a molecular mechanism(s) for this isozyme deficiency, we utilized single-strand conformation polymorphism (SSCP) analysis to detect structural changes in the cDNA. Of 10 SLE subjects, cDNAs from a single subject revealed a shifted band. Sequence analyses demonstrated that a shifted SSCP band from SLE T cells carried heterogeneous transcript mutations, including deletions, transitions and transversions. Most of these transcript mutations are clustered adjacent to GAGAG motifs and CT repeats-regions that are susceptible to transcript editing and/or molecular misreading. By contrast, no genomic mutations were identified. These results suggest the occurrence of mRNA editing and/or defective function of RNA polymerase in a subject with SLE. Mutant RI alpha transcripts are pathophysiolgically significant, for they can encode diverse, aberrant RI alpha isoforms, including truncated, dominant-negative subunits, resulting in deficient PKA-I activity. We propose that deficient PKA-I isozyme activity contributes to the pathogenesis of SLE by hindering effective signal transduction and impairing T cell effector functions.
Laxminarayana
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D
Section on Rheumatology and Clinical Immunology, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Kammer
G M
GM
D003062:Codon / Q000235:genetics; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics*; D018076:DNA, Complementary / Q000032:analysis; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000201:enzymology* / Q000235:genetics* / Q000276:immunology; D009154:Mutation / Q000235:genetics*; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000201:enzymology*; D014158:Transcription, Genetic / Q000235:genetics / Q000276:immunology
D003062:Codon; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D018076:DNA, Complementary; C517834:PRKAR1A protein, human; D012333:RNA, Messenger; D017868:Cyclic AMP-Dependent Protein Kinases