Platelet‐derived growth factor isoforms prevent cell death during starvation of AKR‐2B fibroblasts

Abstract

Confluent AKR-2B fibroblasts rapidly desintegrate upon removal of serum until a final density of approximately 50% of the initial value was reached after 12 h. This density remained unchanged for at least 48 h. Platelet-derived growth factor (PDGF)-BB stimulated more than 95% of these cells to divide. PDGF-AB or -BB added immediately after serum removal caused complete survival of the cells, but did not stimulate cell division as demonstrated by two-dimensional DNA flow cytometry. PDGF-AA was less effective leading to approximately 75% of the initial cell density. This effect could be augmented by the addition of ocadaic acid, a potent phosphatase inhibitor, suggesting that protein phosphorylation plays a role in this process. By using tyrphostin AG807 it was demonstrated that the signaling mechanism for survival requires receptor tyrosine autophosphorylation.

Macrophage Colony-stimulating Factor Promotes Cell Survival through Akt/Protein Kinase B

“…To promote cellular survival, platelet-derived growth factor has been shown to recruit PI3K to the platelet-derived growth factor receptor and to activate the serine/threonine kinase Akt (also known as protein kinase B) (18,19). Similarly, PI3K and Akt are activated in the insulin receptor activation pathway (20), and chimeric receptors constructed of the extracellular domains of M-CSF receptors and the cytoplasmic domains of insulin receptors activate Akt in response to M-CSF (21).…”

ATP and adenosine prevent via different pathways the activation of caspases in apoptotic AKR-2B fibroblasts

“…These cells rapidly disintegrated after serum removal. After a delay of about 90 min death occurs exponentially with a half time of 3.5 h reaching a plateau of 40 ± 50% of the initial cell number after 6 ± 8 h. 26,27 A detailed characterization of morphological changes and biochemical events reveal several features in common with programmed cell death-apoptosis. These include nuclear condensation, membrane blebbing and the involvement of ICE-like proteases in the onset of cell death.…”

“…But surprisingly the protection by PDGF-BB was maintained although this compound provoked a significant increase in [Ca 2+ ] i as described earlier. 26,38 Interestingly the protection by ATP was significantly reduced indicating a participation of [Ca 2+ ] i in the protective signalling pathway by ATP ( Figure 6). …”

“…The antibody was removed by washing six times with washing buffer, and the sheets were prepared for luminescence reaction as described. 26 …”

“…Depending on the cell line, death after serum removal is either immediately initiated (Balbc/3T3) 22 ± 25 or starts after a delay of 90 min (AKR-2B). 26,27 Dying of the cells ceases after 5 ± 6 h with a survival of 10 ± 20% (Balbc/3T3) or 50% (AKR-2B). Morphological changes are quite similar for both cell lines including membrane blebbing and chromatin condensation.…”