title: The p85α regulatory subunit of PI3K mediates cAMP-PKA and retinoic acid             biological effects on MCF7 cell growth and migration.
abstract: Phosphoinositide-3-OH kinase (PI3K) signalling regulates various cellular processes, including cell survival, growth, proliferation and motility, and is among the most frequently mutated pathways in cancer. Although the involvement of p85αPI3K SH2 domain in signal transduction has been extensively studied, the function of the SH3 domain at the N-terminus remains elusive. A serine (at codon 83) adjacent to the N-terminal SH3 domain in the PI3K regulatory subunit p85αPI3K that is phosphorylated by protein kinase A (PKA) in vivo and in vitro has been identified. Virtually all receptors binding p85αPI3K can cooperate with cAMP-PKA signals via phosphorylation of p85αPI3KSer83. To analyse the role of p85αPI3KSer83 in retinoic acid (RA) and cAMP signalling, in MCF7 cells, we used p85αPI3K mutated forms, in which Ser83 has been substituted with alanine (p85A) to prevent phosphorylation or with aspartic acid (p85D) to mimic the phosphorylated residue. We demonstrated that p85αPI3KSer83 is crucial for the synergistic enhancement of RARα/p85αPI3K binding induced by cAMP/RA co-treatment in MCF7 cells. Growth curves, colorimetric MTT assay and cell cycle analysis demonstrated that phosphorylation of p85αPI3KSer83 plays an important role in the control of MCF7 cell proliferation and in RA-induced inhibition of proliferation. Wound healing and transwell experiments demonstrated that p85αPI3KSer83 was also essential both for the control of migratory behaviour and for the reduction of motility induced by RA. This study points to p85αPI3KSer83 as the physical link between different pathways (cAMP-PKA, RA and FAK), and as an important regulator of MCF7 cell proliferation and migration.
authors.affiliation: Department of Experimental Medicine, Sapienza University of Rome,                     Rome, Italy.
authors.forename: Caterina F
authors.initials: CF
authors.lastname: Donini
authors.forename: Erika
authors.initials: E
authors.lastname: Di Zazzo
authors.forename: Candida
authors.initials: C
authors.lastname: Zuchegna
authors.forename: Marina
authors.initials: M
authors.lastname: Di Domenico
authors.forename: Sonia
authors.initials: S
authors.lastname: D'Inzeo
authors.forename: Arianna
authors.initials: A
authors.lastname: Nicolussi
authors.forename: Enrico V
authors.initials: EV
authors.lastname: Avvedimento
authors.forename: Anna
authors.initials: A
authors.lastname: Coppa
authors.forename: Antonio
authors.initials: A
authors.lastname: Porcellini
mesh_terms: D000409:Alanine; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001224:Aspartic Acid; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002417:Cattle; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D009154:Mutation; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D018168:Receptors, Retinoic Acid / Q000187:drug effects / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D012694:Serine; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*; D018909:src Homology Domains
chemical_list: D000970:Antineoplastic Agents; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D001224:Aspartic Acid; D012694:Serine; D014212:Tretinoin; D000242:Cyclic AMP; D058543:Class Ia Phosphatidylinositol 3-Kinase; D017868:Cyclic AMP-Dependent Protein Kinases; D000409:Alanine