Molecular Neurobiology

, Volume 6, Issue 2, pp 239–251

Neuronal compartments and axonal transport of synapsin I

  • Paola Paggi
  • Tamara C. Petrucci

DOI: 10.1007/BF02780556

Cite this article as:
Paggi, P. & Petrucci, T.C. Mol Neurobiol (1992) 6: 239. doi:10.1007/BF02780556


Studies on the transport kinetics and the posttranslational modification of synapsin I in mouse retinal ganglion cells were performed to obtain an insight into the possible factors involved in forming the structural and functional differences between the axon and its terminals. Synapsin I, a neuronal phosphoprotein associated with small synaptic vesicles and cytoskeletal elements at the presynaptic terminals, is thought to be involved in modulating neurotransmitter release. The state of phosphorylation of synapsin I in vitro regulates its interaction with both synaptic vesicles and cytoskeletal components, including microtubules and microfilaments. Here we present the first evidence that in the mouse retinal ganglion cells most synapsin I is transported down the axon, together with the cytomatrix proteins, at the same rate as the slow component b of axonal transport, and is phosphorylated at both the head and tail regions. In addition, our data suggest that, after synapsin I has reached the nerve endings, the relative proportions of variously phosphorylated synapsin I molecules change, and that these changes lead to a decrease in the overall content of phosphorus. These results are consistent with the hypothesis that, in vivo, the phosphorylation of synapsin I along the axon prevents the formation of a dense network that could impair organelle movement. On the other hand, the dephosphorylation of synapsin I at the nerve endings may regulate the clustering of small synaptic vesicles and modulate neurotransmitter release by controlling the availability of small synaptic vesicles for exocytosis.

Index Entries

Neuronal compartments posttranslational modification of synapsin I slow axonal transport synaptic vesicles neuronal protein phosphorylation mouse optic system transport kinetics of synapsin I 

Copyright information

© The Humana Press, Inc 1992

Authors and Affiliations

  • Paola Paggi
    • 1
  • Tamara C. Petrucci
    • 2
  1. 1.Dipartimento di Biologia Cellulare e dello Sviluppo Università ‘La Sapienza’RomeItaly
  2. 2.Laboratorio di Biologia CellulareIstituto Superiore di SanitàRomeItaly