HIP/PAP, a C-type lectin overexpressed in hepatocellular carcinoma, binds the RII alpha regulatory subunit of cAMP-dependent protein kinase and alters the cAMP-dependent protein kinase signalling.
HIP/PAP is a C-type lectin overexpressed in hepatocellular carcinoma (HCC). Pleiotropic biological activities have been ascribed to this protein, but little is known about the function of HIP/PAP in the liver. In this study, therefore, we searched for proteins interacting with HIP/PAP by screening a HCC cDNA expression library. We have identified the RII alpha regulatory subunit of cAMP-dependent protein kinase (PKA) as a partner of HIP/PAP. HIP/PAP and RII alpha were coimmunoprecipitated in HIP/PAP expressing cells. The biological relevance of the interaction between these proteins was established by demonstrating, using fractionation methods, that they are located in a same subcellular compartment. Indeed, though HIP/PAP is a protein secreted via the Golgi apparatus we showed that a fraction of HIP/PAP escaped the secretory apparatus and was recovered in the cytosol. Basal PKA activity was increased in HIP/PAP expressing cells, suggesting that HIP/PAP may alter PKA signalling. Indeed, we showed, using a thymidine kinase-luciferase reporter plasmid in which a cAMP responsive element was inserted upstream of the thymidine kinase promoter, that luciferase activity was enhanced in HIP/PAP expressing cells. Thus our findings suggest a novel mechanism for the biological activity of the HIP/PAP lectin.
Demaugre
France
F
INSERM U370 CHU Necker Enfants Malades, 75015 Paris, France. demaugre@necker.fr
Philippe
Yannick
Y
Sar
Sokavuth
S
Pileire
Bernard
B
Christa
Laurence
L
Lasserre
Chantal
C
Brechot
Christian
C
D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000242:Cyclic AMP / Q000378:metabolism*; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015723:Gene Library; D006056:Golgi Apparatus; D006801:Humans; D047468:Immunoprecipitation; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D000073718:Pancreatitis-Associated Proteins; D010766:Phosphorylation; D015398:Signal Transduction; D013347:Subcellular Fractions; D013937:Thymidine Kinase / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D037181:Lectins, C-Type; C517837:PRKAR2B protein, human; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D000242:Cyclic AMP; D008156:Luciferases; D013937:Thymidine Kinase; D017868:Cyclic AMP-Dependent Protein Kinases