Catalytic subunit of protein kinase A is an interacting partner of the inflammation-responsive transcription factor serum amyloid A-activating factor-1
Bk. Ray et al., Catalytic subunit of protein kinase A is an interacting partner of the inflammation-responsive transcription factor serum amyloid A-activating factor-1, J IMMUNOL, 167(4), 2001, pp. 2343-2348
Serum amyloid A-activating factor-1 (SAF-1) is a zinc finger transcription
factor that is activated by many mediators of inflammation including IL-1,
IL-6, and bacterial LPS. However, the mechanism of activation is not fully
understood. To identify possible activation partners for SAF-I, we used a y
east two-hybrid system that detected interaction between the catalytic subu
nit of cyclic AMP-dependent protein kinase (PKA-C alpha) and SAF-I. Immunof
luorescence and combined immunoprecipitation-Western blot analyses revealed
colocalization and interaction between SAF-I and PKA-C alpha. In vivo evid
ence of SAF-1 and PKA-C alpha interaction was further revealed by coimmunop
recipitation of these two proteins in cAMP-activated liver cells. We furthe
r show that SAF-1 is phosphorylated in vitro by PKA-C alpha and that additi
on of cAMP markedly induces in vivo phosphorylation of SAF-1 and transcript
ion of SAF-regulated reporter genes. These results showed that SAF1-PICA-C
alpha interaction is involved in functional activation of SAF-I.