Thrombin receptor peptides induce shape change in neonatal murine astrocytes in culture.
Astrocytes appear star-shaped in the brain, increasingly so after injury. When astroglia are cultured in serum-containing medium, they exhibit a flat, fibroblast-like morphology. In serum-free medium, astrocytes become stellate, with many long processes. The serine protease alpha-thrombin mimics the effects of serum at subnanomolar concentrations, whereas the thrombin-inhibiting serpin, protease nexin I (PNI), reverses the thrombin effect. In our current experiments, murine neonatal spinal cord astrocytes became stellate after 4 hr in serum-free medium, while cortical astrocytes required 12 hr in serum-free medium for stellation. Astrocytes from either region flattened after 60 min in medium containing 3.0 to 300 pM proteolytically active human alpha-thrombin. After 12 hr in thrombin-containing medium, 98% of the astrocytes had a flattened morphology. No flattening occurred if alpha-thrombin was replaced by gamma-thrombin, which has its fibrinogen-recognition exosite disrupted. PNI added at 1 nM to serum-containing medium caused stellation after 3 hr, and astroglia were 50% stellate by 12 hr. The effect of thrombin was mimicked by a 7-amino acid peptide (TRP-7) from the cleavage site of the human thrombin receptor. This peptide caused 40% of the astrocytes in serum-free medium to exhibit a flattened morphology after 6 hr. PNI had no effect on TRP-7 action on astrocytes. These results indicate that astrocytes possess a cell-surface receptor for thrombin, similar to that described for platelets, endothelial cells, and neurons.
Beecher
K L
KL
Neurobiology Research Lab, Veterans Affairs Medical Center, Kansas City, Missouri 64128.
Andersen
T T
TT
Fenton
J W
JW
Festoff
B W
BW
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000648:ultrastructure; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology*; D018179:Receptors, Thrombin / Q000737:chemistry*; D013116:Spinal Cord / Q000166:cytology; D013917:Thrombin / Q000494:pharmacology
D016895:Culture Media, Serum-Free; D010446:Peptide Fragments; D018179:Receptors, Thrombin; D013917:Thrombin