Effects of cAMP on intercellular coupling and osteoblast differentiation.
Bone-forming cells are organized in a multicellular network interconnected by gap junctions. Direct intercellular communication via gap junctions is an important component of bone homeostasis, coordinating cellular responses to external signals and promoting osteoblast differentiation. The cAMP pathway, a major intercellular signal transduction mechanism, regulates osteoblastic function and metabolism. We investigated the effects of this second messenger on junctional communication and on the expression of differentiation markers in human HOBIT osteoblastic cells. Increased levels of cAMP induce posttranslational modifications (i.e., phosphorylations) of connexin43 and enhancement of gap junction assembly, resulting in an increased junctional permeance to Lucifer yellow and to a positive modulation of intercellular Ca(2+) waves. Increased intercellular communication, however, was accompanied by a parallel decrease of alkaline phosphatase activity and by an increase of osteocalcin expression. cAMP-dependent stimulation of cell-to-cell coupling induces a complex modulation of bone differentiation markers.
Romanello
M
M
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università di Trieste, via Licio Giorgieri 1, Trieste, I-34127, Italy.
Moro
L
L
Pirulli
D
D
Crovella
S
S
D'Andrea
P
P
D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000943:Antigens, Differentiation / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D018031:Connexin 43 / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D000943:Antigens, Differentiation; D018031:Connexin 43; D010726:Phosphodiesterase Inhibitors; D012333:RNA, Messenger; D015675:Osteocalcin; D005576:Colforsin; D000242:Cyclic AMP; D000469:Alkaline Phosphatase