The two-receptor system PAR-1/PAR-4 mediates alpha-thrombin-induced [Ca(2+)](i) mobilization in human astrocytoma cells.
The proteinase-activated receptor 1 (PAR-1) was characterized as a functional receptor for thrombin in cells from different brain tumor entities. Whether PAR-1 alone accounts for thrombin-induced effects in human cancer cells, or whether other PAR contribute is unknown. We established primary cultures from two neurosurgically removed human astrocytomas and investigated intracellular signaling roles of PAR-1 and PAR-4 by estimating the effect of alpha-thrombin and PAR-activating peptides on [Ca(2+)](i) mobilization in single astrocytoma cells. alpha-Thrombin or the PAR-1-activating peptide SFLLRN induced a transient calcium mobilization. This suggests the involvement of PAR-1 in alpha-thrombin-induced calcium signaling in human astrocytoma cells. In addition, a second, PAR-4-dependent, mechanism exists. This was deduced from the findings that a further calcium signal could be observed in human astrocytoma cells stimulated with alpha-thrombin after SFLLRN and the PAR-4-activating peptide GYPGQV also induced a calcium response. In addition, the observation that trypsin, known to activate both PAR-2 and PAR-4, but not the specifically PAR-2-activating peptide SLIGRL induced calcium signaling is a further indication of functional PAR-4-type thrombin receptors in human astrocytoma cells. This is the first report demonstrating a signaling role for a dual thrombin receptor system in human tumor cells.
Kaufmann
R
R
Research Group "Pharmacological Hemostaseology", Medical Faculty at the Friedrich Schiller University Jena, Drackendorfer Str. 1, D-07747 Jena, Germany. rol@leech.mpg.uni-jena.de
Patt
S
S
Zieger
M
M
Kraft
R
R
Tausch
S
S
Henklein
P
P
Nowak
G
G
D051017:Apoptosis Regulatory Proteins; D001254:Astrocytoma / Q000473:pathology*; D001932:Brain Neoplasms / Q000473:pathology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D051017:Apoptosis Regulatory Proteins; D015220:Calcium Channels; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; C101296:prostate apoptosis response-4 protein; D013917:Thrombin; D002118:Calcium