Diminished levels of protein kinase A RI alpha and RI beta transcripts andproteins 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 inv estigate the mechanism of this deficient isozyme activity,we hypothesized t hat reduced amounts of type I regulatory (RI) isoform transcripts, RI alpha and RI beta, may be associated with a diminution of RI alpha and/or RI bet a 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, s ix subjects with primary Sjogren's syndrome (SS), and three subjects with S S/SLE overlap, RT-PCR revealed that normal, SS, SS/SLE, and SLE T cells exp ressed mRNAs for all seven R and catalytic (C) subunit isoforms, Quantifica tion of mRNAs by competitive PCR revealed that the ratio of RI alpha mRNA t o RI beta mRNA in normal T cells was 3.4:1, In SLE T cells there were 20 an d 49% decreases in RI alpha and RI beta mRNAs (RI beta; p = 0.008), respect ively, resulting in an RI alpha:RI beta mRNA of 5.3:1, SS/SLE T cells showe d a 72.5% decrease in RI beta mRNA compared with normal controls (p = 0.01) , Immunoblotting of normal T cell RI alpha and RI beta proteins revealed a ratio of RI alpha:RI beta of 3.2:1, In SLE T cells, there was a 30% decreas e in RI alpha protein (p = 0.002) and a 65% decrease in RI beta protein (p < 0.001), shifting the ratio of RI alpha:RI beta protein to 6.5:1, T cells from 25% of SLE subjects lacked any detectable RI beta protein. Analysis of several lupus T cell lines demonstrated a persistent deficiency of both pr oteins, excluding a potential effect of disease activity. In conclusion, re duced expression of RI alpha and RI beta transcripts is associated with a d ecrement in RI alpha and RI beta proteins and may contribute to deficient t ype I protein kinase A isozyme activity in SLE T cells.