Diminished levels of protein kinase A RI alpha and RI beta transcripts and proteins in systemic lupus erythematosus T lymphocytes.
Deficient type I protein kinase A phosphotransferase activity occurs in the T cells of 80% of subjects with systemic lupus erythematosus (SLE). To investigate the mechanism of this deficient isozyme activity, we hypothesized that reduced amounts of type I regulatory (RI) isoform transcripts, RIalpha and RIbeta, may be associated with a diminution of RIalpha and/or RIbeta protein. Sixteen SLE subjects with a mean (+/-1 SD) SLE disease activity index of 12.4 +/- 7.2 were studied. Controls included 16 normal subjects, six subjects with primary Sjögren's syndrome (SS), and three subjects with SS/SLE overlap. RT-PCR revealed that normal, SS, SS/SLE, and SLE T cells expressed mRNAs for all seven R and catalytic (C) subunit isoforms. Quantification of mRNAs by competitive PCR revealed that the ratio of RIalpha mRNA to RIbeta mRNA in normal T cells was 3.4:1. In SLE T cells there were 20 and 49% decreases in RIalpha and RIbeta mRNAs (RIbeta; p = 0.008), respectively, resulting in an RIalpha:RIbeta mRNA of 5.3:1. SS/SLE T cells showed a 72.5% decrease in RIbeta mRNA compared with normal controls (p = 0.01). Immunoblotting of normal T cell RIalpha and RIbeta proteins revealed a ratio of RIalpha:RIbeta of 3.2:1. In SLE T cells, there was a 30% decrease in RIalpha protein (p = 0.002) and a 65% decrease in RIbeta protein (p < 0.001), shifting the ratio of RIalpha:RIbeta protein to 6.5:1. T cells from 25% of SLE subjects lacked any detectable RIbeta protein. Analysis of several lupus T cell lines demonstrated a persistent deficiency of both proteins, excluding a potential effect of disease activity. In conclusion, reduced expression of RIalpha and RIbeta transcripts is associated with a decrement in RIalpha and RIbeta proteins and may contribute to deficient type I protein kinase A isozyme activity in SLE T cells.
Laxminarayana
D
D
Section on Rheumatology, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. dlaxmina@wfubmc.edu
Khan
I U
IU
Mishra
N
N
Olorenshaw
I
I
Taskén
K
K
Kammer
G M
GM
D000328:Adult; D000368:Aged; D002460:Cell Line; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D054753:Cyclic AMP-Dependent Protein Kinase RIbeta Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D005796:Genes; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008180:Lupus Erythematosus, Systemic / Q000201:enzymology* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D013601:T-Lymphocytes / Q000737:chemistry / Q000201:enzymology*; D014158:Transcription, Genetic / Q000276:immunology*
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D054753:Cyclic AMP-Dependent Protein Kinase RIbeta Subunit; D007527:Isoenzymes; C517834:PRKAR1A protein, human; C517766:PRKAR1B protein, human; D017868:Cyclic AMP-Dependent Protein Kinases