S-100 protein in synapses of the central nervous system

Abstract

THE brain-specific S-100 protein¹ is predominantly localised in glial cells in the central nervous system and is synthesised by glial cells in tissue culture^2–5. S-100 is, however, also present in neurones^6–9, located in both the neuronal perikaryon and the nucleus^6,9–11. It has been proposed that the protein is transported along the axon¹⁰ although the presence of S-100 in the Schwann cell^12,13 calls for confirmation of an intra-axonal localisation of the protein. Approximately 90% of the S-100 in the brain is easily soluble and extracted by water^14–15, but an additional small amount can be extracted from the particulate matter with n-pentanol. Rusca et al.¹⁴ showed a further release 5–7% of the S-100 from whole beef brain, and Haglid et al.¹³ extracted 7% from human grey matter and 3% from white matter with n-pentanol. The percentage of total S-100 which remained bound to the particulate matter after water extraction was considerably higher in neuronal perikarya than in glial cells (manuscript in preparation). We have investigated the ultrastructural location of the relatively large amounts of membrane-bound neuronal S-100.