Exo-endocytotic recycling of synaptic vesicles in developing processes of cultured hippocampal neurons

Michela Matteoli, Kohji Takei, Mark S. Perin, Thomas C. Südhof, Pietro De Camilli

Research output: Contribution to journalArticle

Abstract

In mature neurons synaptic vesicles (SVs) undergo cycles of exo-endocytosis at synapses. It is currently unknown whether SV exocytosis and recycling occurs also in developing axons prior to synapse formation. To address this question, we have developed an immunocytochemical assay to reveal SV exo-endocytosis in hippocampal neurons developing in culture. In this assay antibodies directed against the lumenal domain of synaptotagmin I (Syt I), an intrinsic membrane protein of SVs, are used to reveal exposure of SV membranes at the cell surface. Addition of antibodies to the culture medium of living neurons for 1 hr at 37°C resulted in their rapid and specific internal ization by all neuronal processes and, particularly, by axons. Double immunofluorescence and electron microscopy immunocytochemistry indicated that the antibodies were retained within SVs in cell processes and underwent cycles of exo-endocytosis in parallel with SV membranes. In contrast, another endocytotic marker, wheat germ agglutinin, was rapidly cleared from the processes and transported to the cell body. Antibody-labeled SVs were still present in axons several days after antibody loading and became clustered at presynaptic sites in parallel with synaptogenesis. These results demonstrate that SVs undergo multiple cycles of exo-endocytosis in developing neuronal processes irrespective of the presence of synaptic contacts.

Original languageEnglish
Pages (from-to)849-861
Number of pages13
JournalJournal of Cell Biology
Volume117
Issue number4
Publication statusPublished - May 1992

ASJC Scopus subject areas

  • Cell Biology

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