Increase of intracellular free Ca2+ in microglia activated by prion protein fragment.
A synthetic peptide consisting of amino acid residues 106 to 126 of the human prion protein (PrPc) that forms fibrils in vitro is toxic to cultured neurons. We have previously shown that the neurotoxic effect of this peptide is related to microglia activation (Brown et al., 1996a). For closer insight into this process of activation, we investigated the effect of the peptide on the intracellular free Ca2+ concentration ([Ca2+]i) in cultured microglia using Fura-2. Cultured microglia from wild-type as well as from PrPc gene-ablated mice (Prn-p0/0) responded to exposure to PrP106-126 with an increase in intracellular free calcium within 30 min. We observed two types of responses. Both in wild-type and Prn-p0/0 mice about half of the tested cells presented a small and often transient calcium increase after peptide application which was found to be independent of the extracellular calcium concentration. However, a further 33% of wild-type cells showed a strong and often permanent calcium increase depending on the extracellular calcium concentration, which was only rarely observed in Prn-p0/0 cells. To determine whether the response depended on the activation state of the microglia, we also examined LPS-treated activated microglia. The character of the calcium response remained unchanged, but significantly fewer cells responded. Our findings demonstrate the earliest reaction of microglia to a PrP fragment known to date.
Herms
J W
JW
Department of Neuropathology, University of Göttingen, Germany.
Madlung
A
A
Brown
D R
DR
Kretzschmar
H A
HA
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D011328:Prions / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism
D005609:Free Radicals; D008070:Lipopolysaccharides; D010446:Peptide Fragments; D011328:Prions; D013481:Superoxides; D002118:Calcium