Potentiation of angiogenic switch in capillary endothelial cells by cAMP: A cross-talk between up-regulated LLO biosynthesis and the HSP-70 expression.
During tumor growth and invasion, the endothelial cells from a relatively quiescent endothelium start proliferating. The exact mechanism of switching to a new angiogenic phenotype is currently unknown. We have examined the role of intracellular cAMP in this process. When a non-transformed capillary endothelial cell line was treated with 2 mM 8Br-cAMP, cell proliferation was enhanced by approximately 70%. Cellular morphology indicated enhanced mitosis after 32-40 h with almost one-half of the cell population in the S phase. Bcl-2 expression and caspase-3, -8, and -9 activity remained unaffected. A significant increase in the Glc(3)Man(9)GlcNAc(2)-PP-Dol biosynthesis and turnover, Factor VIIIC N-glycosylation, and cell surface expression of N-glycans was observed in cells treated with 8Br-cAMP. Dol-P-Man synthase activity in the endoplasmic reticulum membranes also increased. A 1.4-1.6-fold increase in HSP-70 and HSP-90 expression was also observed in 8Br-cAMP treated cells. On the other hand, the expression of GRP-78/Bip was 2.3-fold higher compared to that of GRP-94 in control cells, but after 8Br-cAMP treatment for 32 h, it was reduced by 3-fold. GRP-78/Bip expression in untreated cells was 1.2-1.5-fold higher when compared with HSP-70 and HSP-90, whereas that of the GRP-94 was 1.5-1.8-fold lower. After 8Br-cAMP treatment, GRP-78/Bip expression was reduced 4.5-4.8-fold, but the GRP-94 was reduced by 1.5-1.6-fold only. Upon comparison, a 2.9-fold down-regulation of GRP-78/Bip was observed compared to GRP-94. We, therefore, conclude that a high level of Glc(3)Man(9)GlcNAc(2)-PP-Dol, resulting from 8Br-cAMP stimulation up-regulated HSP-70 expression and down-regulated that of the GRP-78/Bip, maintained adequate protein folding, and reduced endoplasmic reticulum stress. As a result capillary endothelial cell proliferation was induced.
Martínez
Juan A
JA
Department of Biochemistry, School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936-5067, USA.
Tavárez
José J
JJ
Oliveira
Caroline M
CM
Banerjee
Dipak K
DK
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002196:Capillaries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002240:Carbohydrate Sequence; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism; D005169:Factor VIII; D006031:Glycosylation; D018840:HSP70 Heat-Shock Proteins / Q000187:drug effects / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000187:drug effects / Q000378:metabolism; D008364:Mannosyltransferases / Q000187:drug effects / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D008969:Molecular Sequence Data; D018919:Neovascularization, Physiologic; D011105:Polyisoprenyl Phosphate Sugars / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D013925:Thromboplastin / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation
C066723:Glc(3)Man(9)(GlcNAc)(2)-diphosphate-dolichol; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D011105:Polyisoprenyl Phosphate Sugars; D011134:Polysaccharides; D019253:Proto-Oncogene Proteins c-bcl-2; D015124:8-Bromo Cyclic Adenosine Monophosphate; D005169:Factor VIII; D013925:Thromboplastin; D000242:Cyclic AMP; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase; D020169:Caspases