Introduction of macromolecules into synaptosomes using electroporation

Altered conformation of α-synuclein drives dysfunction of synaptic vesicles in a synaptosomal model of Parkinson's disease

While misfolding of alpha-synuclein (αSyn) is central to the pathogenesis of Parkinson's disease (PD), fundamental questions about its structure and function at the synapse remain unanswered. We examine synaptosomes from non-transgenic and transgenic mice expressing wild-type human αSyn, the E46K fPD-causing mutation, or an amplified form of E46K ("3K"). Synaptosomes from mice expressing the 3K mutant show reduced Ca²⁺-dependent vesicle exocytosis, altered synaptic vesicle ultrastructure, decreased SNARE complexes, and abnormal levels of certain synaptic proteins. With our intra-synaptosomal nuclear magnetic resonance (NMR) method, we reveal that WT αSyn participates in heterogeneous interactions with synaptic components dependent on endogenous αSyn and synaptosomal integrity. The 3K mutation markedly alters these interactions. The synaptic microenvironment is necessary for αSyn to reach its native conformations and establish a physiological interaction network. Its inability to populate diverse conformational ensembles likely represents an early step in αSyn dysfunction that contributes to the synaptotoxicity observed in synucleinopathies.

Low-frequency ultrasound combined with microbubbles improves gene transfection in prostate cancer cells in vitro and in vivo

OBJECTIVES

The aim of this study is to explore whether low-frequency ultrasound combined with microbubbles improves pEGFP genes transfection into human prostate cancer cells.

METHODS

Ultrasound with frequency of 80 kHz and duty cycle of 50% was adopted in the study; in in vitro experiments, cell lysis, and membrane damage were evaluated after ultrasound exposure; and the membrane continuity and transfection efficiency were observed by transmission electron microscope and laser scanner, respectively. Human prostate cancer xenograft models were exposed to ultrasound and transfection efficiency and histological examination were analyzed.

RESULTS

Compared with the control group, ultrasound combined with microbubbles significantly improves gene transfection efficiency (P < .05). In in vitro study, ultrasound combined with microbubbles resulted in cell lysis and the interruption of cell membrane continuity, and its average transfection efficiency was 9.9%; the green fluorescence intensity was 15.2% in the ultrasound combined with microbubbles group in vivo; both values were higher than that in the control group (P < .05).

CONCLUSION

Low-frequency ultrasound combined with microbubbles could be used as a method to promote gene transfection in prostate cancer cells.

Reduced aspartate release from rat hippocampal synaptosomes loaded with Clostridial toxin light chain by electroporation: evidence for an exocytotic mechanism

Aspartate can be released from certain hippocampal pathways along with glutamate or GABA. Although aspartate immunoreactivity has been localized to synaptic vesicles and aspartate release is Ca(2+)-dependent, there has been no clear evidence favoring an exocytotic mechanism. In particular, pretreatment with Clostridial toxins has not consistently inhibited aspartate release, even when release of glutamate from the same tissue samples was markedly inhibited. To address this issue directly, rat hippocampal synaptosomes were permeabilized transiently by electroporation in the presence of active or inactivated Clostridial toxin light chains. Loading rat hippocampal synaptosomes with the active light chain of tetanus toxin or of botulinum neurotoxins A, B or C reduced the K(+)-evoked release of aspartate at least as much as that of glutamate. These results confirm that aspartate is released by exocytosis in rat hippocampus.

Release of tritiated agmatine from spinal synaptosomes

Intrathecal agmatine (decarboxylated arginine) moderates induction of neuropathic pain, spinal cord injury, and opioid tolerance in rodents. An endogenous central nervous system molecule and N-methyl-D-aspartate receptor antagonist/nitric oxide synthase inhibitor, agmatine may be a neuromodulator. We evaluated depolarization-induced release of agmatine from purified spinal nerve terminals (synaptosomes). Agmatine immunoreactivity was observed colocalized or closely apposed to some synaptophysin- and/or synaptotagmin-labeled structures. A temperature- and concentration-dependent uptake of [3H]-agmatine into synaptosomes was observed, consistent with an uptake mechanism. Potassium-induced depolarization resulted in release of [3H]-agmatine from the synaptosomes in a Ca2+-dependent manner, consistent with a neuromodulatory function. These results agree with previous reports of agmatine uptake into synaptosomes of the brain and extend those results to include stimulated release and a spinal site of activity.