Exchange and redistribution dynamics of the cytoskeleton of the active zone molecule bassoon.
Presynaptic sites typically appear as varicosities (boutons) distributed along axons. Ultrastructurally, presynaptic boutons lack obvious physical barriers that separate them from the axon proper, yet activity-related and constitutive dynamics continuously promote the "reshuffling" of presynaptic components and even their dispersal into flanking axonal segments. How presynaptic sites manage to maintain their organization and individual characteristics over long durations is thus unclear. Conceivably, presynaptic tenacity might depend on the active zone (AZ), an electron-dense specialization of the presynaptic membrane, and particularly on the cytoskeletal matrix associated with the AZ (CAZ) that could act as a relatively stable "core scaffold" that conserves and dictates presynaptic organization. At present, however, little is known on the molecular dynamics of CAZ molecules, and thus, the factual basis for this hypothesis remains unclear. To examine the stability of the CAZ, we studied the molecular dynamics of the major CAZ molecule Bassoon in cultured hippocampal neurons. Fluorescence recovery after photobleaching and photoactivation experiments revealed that exchange rates of green fluorescent protein and photoactivatable green fluorescent protein-tagged Bassoon at individual presynaptic sites are very low (tau > 8 h). Exchange rates varied between boutons and were only slightly accelerated by stimulation. Interestingly, photoactivation experiments revealed that Bassoon lost from one synapse was occasionally assimilated into neighboring presynaptic sites. Our findings indicate that Bassoon is engaged in relatively stable associations within the CAZ and thus support the notion that the CAZ or some of its components might constitute a relatively stable presynaptic core scaffold.
Tsuriel
Shlomo
S
Department of Physiology, Technion Faculty of Medicine, Lorry Lokey Interdisciplinary Center for Life Sciences and Engineering, The Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel.
Fisher
Arava
A
Wittenmayer
Nina
N
Dresbach
Thomas
T
Garner
Craig C
CC
Ziv
Noam E
NE
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D017711:Nonlinear Dynamics; D010775:Photic Stimulation / Q000379:methods; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014162:Transfection / Q000379:methods
C498441:Bsn protein, mouse; D018691:Excitatory Amino Acid Antagonists; C092350:FM 4-64; D005456:Fluorescent Dyes; D009419:Nerve Tissue Proteins; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D049452:Green Fluorescent Proteins; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate