Cell-to-cell communication in osteoblastic networks: cell line-dependent hormonal regulation of gap junction function.
We have characterized the distribution, expression, and hormonal regulation of gap junctions in primary cultures of rat osteoblast-like cells (ROBs), and three osteosarcoma cell lines, ROS 17/2.8, UMR-106, and SAOS-2, and a continuous osteoblastic cell line, MC3T3-E1. All cell lines we examined were functionally coupled. ROS 17/2.8 were the more strongly coupled, while ROB and MC3T3-E1 were moderately coupled and UMR-106 and SAOS-2 were weakly coupled. Exposure to parathyroid hormone (PTH) for 1 h increased functional coupling in ROB cells in a concentration-dependent manner. Furthermore, PTH(3-34), an analog of PTH with binds to the PTH receptor and thus attenuates PTH-stimulated cAMP accumulation, also attenuated PTH-stimulated functional coupling in ROB. This suggests that PTH increases functional coupling partly through a cAMP-dependent mechanism. A 1 h exposure to PTH did not affect coupling in ROS 17/2.8, UMR-106, MC3T3-E1, or SAOS-2. To examine whether connexin43 (Cx43), a specific gap junction protein, is present in functionally coupled osteoblastic cells, we characterized Cx43 distribution and expression. Indirect immunofluorescence with antibodies to Cx43 revealed that ROS 17/2.8, ROB, and to a lesser extent MC3T3-E1 and UMR-106, expressed Cx43 immunoreactivity. SAOS-2 showed little if any Cx43 immunoreactivity. Cx43 mRNA and Cx43 protein were detected by Northern blot analysis and immunoblot analysis, respectively, in all cell lines examined, including SAOS-2. Our findings suggest that acute exposure to PTH regulates gap junction coupling, in a cell-line dependent manner, in osteoblastic cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Donahue
H J
HJ
Department of Orthopedics, Pennsylvania State University College of Medicine, Hershey, USA.
McLeod
K J
KJ
Rubin
C T
CT
Andersen
J
J
Grine
E A
EA
Hertzberg
E L
EL
Brink
P R
PR
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001859:Bone Neoplasms / Q000473:pathology; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D017629:Gap Junctions / Q000187:drug effects* / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D012516:Osteosarcoma / Q000473:pathology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D019379:Teriparatide; D014407:Tumor Cells, Cultured
D018031:Connexin 43; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012333:RNA, Messenger; D019379:Teriparatide; C031617:parathyroid hormone (3-34)