Potentiation of angiogenic switch in capillary endothelial cells by cAMP: A cross-talk between up-regulated LLO biosynthesis and the HSP-70 expression |
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Authors: | Juan A Martínez José J Tavárez Caroline M Oliveira Dipak K Banerjee |
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Institution: | (1) Department of Biochemistry, School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936-5067, USA |
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Abstract: | 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 ∼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 Glc3Man9GlcNAc2-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 Glc3Man9GlcNAc2-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. |
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Keywords: | Angiogenesis Lipid-linked oligosaccharide N-linked glycoprotein Mannosylphosphodolichol synthase EC 2 4 1 83 cAMP Breast cancer |
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