Functional role of bone morphogenetic protein-4 in isolated canine parietal cells.
Bone morphogenetic protein (BMP)-4 is an important regulator of cellular growth and differentiation. Expression of BMP-4 has been documented in the gastric mucosa. We reported that incubation of canine parietal cells with EGF for 72 h induced both parietal cell morphological transformation and inhibition of H(+)/K(+)-ATPase gene expression through MAPK-dependent mechanisms. We explored the role of BMP-4 in parietal cell maturation and differentiation. Moreover, we investigated if BMP-4 modulates the actions of EGF in parietal cells. H(+)/K(+)-ATPase gene expression was examined by Northern blots and quantitative RT-PCR. Acid production was assessed by measuring the uptake of [(14)C]aminopyrine. Parietal cell apoptosis was quantitated by Western blots with anti-cleaved caspase 3 antibodies and by counting the numbers of fragmented, propidium iodide-stained nuclei. MAPK activation and Smad1 phosphorylation were measured by Western blots with anti-phospho-MAPK and anti-phospho-Smad1 antibodies. Parietal cell morphology was examined by immunohistochemical staining of cells with anti-H(+)/K(+)-ATPase alpha-subunit antibodies. BMP-4 stimulated Smad1 phosphorylation and induced H(+)/K(+)-ATPase gene expression. BMP-4 attenuated EGF-mediated inhibition of H(+)/K(+)-ATPase gene expression and blocked EGF induction of both parietal cell morphological transformation and MAPK activation. Incubation of cells with BMP-4 enhanced histamine-stimulated [(14)C]aminopyrine uptake. BMP-4 had no effect on parietal cell apoptosis, whereas TGF-beta stimulated caspase-3 activation and nuclear fragmentation. In conclusion, BMP-4 promotes the induction and maintenance of a differentiated parietal cell phenotype. These findings may provide new clues for a better understanding of the mechanisms that regulate gastric epithelial cell growth and differentiation.
Nitsche
Hildegard
H
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI 48109-0682, USA.
Ramamoorthy
Saravanan
S
Sareban
Mahdi
M
Pausawasdi
Nonthalee
N
Todisco
Andrea
A
D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D048430:Cell Shape; D002478:Cells, Cultured; D004285:Dogs; D004815:Epidermal Growth Factor / Q000378:metabolism; D005744:Gastric Acid / Q000378:metabolism; D005748:Gastric Fundus / Q000166:cytology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D006632:Histamine / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D010295:Parietal Cells, Gastric / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D012333:RNA, Messenger; D051896:Smad Proteins, Receptor-Regulated; D016212:Transforming Growth Factor beta; D000632:Aminopyrine; D004815:Epidermal Growth Factor; D006632:Histamine; D019950:Mitogen-Activated Protein Kinase 1; D017506:H(+)-K(+)-Exchanging ATPase