title: PKA-dependent and independent cAMP signaling in 3T3-L1 fibroblasts differentiation.
abstract: Adipogenesis is stimulated in 3T3-L1 fibroblast by a combination of insulin, dexamethasone, and methylisobutylxanthine (MIX). Mitotic clonal expansion (MCE) precedes differentiation of 3T3-L1 fibroblast to adipocytes. MIX increases cAMP content, which is the activator of protein kinase A (PKA). However, PKA-independent cAMP signaling has also been described. In this paper, it was found that H89, an inhibitor of PKA, was able to block MCE but not differentiation of 3T3-L1 fibroblast. Consistently, MCE did not occur in the absence of MIX in the differentiation mixture but was recovered by overexpression of a catalytic subunit of PKA. In addition, the transfection of 3T3-L1 fibroblast with a dominant-negative mutant of PKA inhibited MCE. On the other hand, differentiation of 3T3-L1 fibroblast to adipocytes did not occur when MIX was not present in the differentiation mixture and it could not be recovered by overexpression of a catalytic subunit of PKA. Differentiation was restored by addition of either dibutyryl-cAMP (db-cAMP) or 8 CPT-2 Me-cAMP. The latter activates cAMP-EPAC but not PKA signaling. These results indicate that cAMP-PKA-independent signaling, is required for 3T3-L1 fibroblasts differentiation to adipocytes and MIX signaling through cAMP-PKA is necessary for MCE, although MCE is not essential for adipogenesis.
authors.affiliation: Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Claudia N
authors.initials: CN
authors.lastname: Martini
authors.forename: Maria V
authors.initials: MV
authors.lastname: Plaza
authors.forename: Maria del C
authors.initials: Mdel C
authors.lastname: Vila
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D007328:Insulin; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; C053907:8-cyclopentyl-1,3-dimethylxanthine; D003907:Dexamethasone; D013806:Theophylline; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D015056:1-Methyl-3-isobutylxanthine