Abstract
We have investigated the influence of the neural cell adhesion molecules
L1 and N-CAM on second messenger systems using a PC12 rat pheochromocytoma
cell line as a model and triggering cell surface receptors by specific
antibody binding. Antibodies directed against L1 and N-CAM, but not
against other cell surface components, reduce intracellular levels
of the inositol phosphates IP2 and IP3, while intracellular levels
of cAMP are unaffected. Antibodies against L1 and N-CAM also reduce
intracellular pH and increase intracellular Ca2+ by opening Ca2+
channels in a pertussis toxin-inhibitable manner, suggesting the
involvement of a G protein in the signal transduction process. Cross-linking
of the adhesion molecules on the surface membrane is not required
for the effects to occur. Furthermore, adhesion of single PC12 cells
to each other elicits effects on intracellular pH and Ca2+ similar
to those seen after application, underscoring the physiological significance
of the observed changes.
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