| Abstract No.: | A-B1035 |
| Country: | Canada |
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| Title: | PDLIM5 DOES NOT INTERACT DIRECTLY WITH CAV2.2 AT THE PRESYNAPTIC TERMINAL |
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| Authors/Affiliations: | 1 Sabiha Gardezi*; 1 Elise F. Stanley
1 Toronto Western Hospital, ON, Canada
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| Content: | N type calcium channels play a key role in the triggering of transmitter release at presynaptic terminals and hence, signaling pathways that regulate their excitability are of considerable interest as potential modulators of synaptic strength. A recent report (Maeno-Hikichi et al., 2003) examined the interaction of this channel with the cytoplasmic protein PDLIM5, a protein recently identified as a risk factor in psychiatric disorders. Based primarily on pull-down studies using the C terminal region of the channel they concluded that PDLIM5 scaffolds CaV2.2 to protein kinase C (PKC), a known channel modulator. Objectives: We set out to test the hypothesis that PDLIM5 interacts with CaV2.2 at intact presynaptic terminals. Materials and Methods: First, we made a lysate from fresh purified rat brain synaptosomes and used anti-CaV2.2 and anti-PDLIM5 antibodies to test if these two proteins co-precipitate. Second, we isolated giant calyx-type presynaptic terminals from the chick ciliary ganglion and used quantitative immunocytochemistry to test if the CaV2.2 and PDLIM5 are parts of a common complex in situ. Results: Immunoprecipitation of PDLIM5 or CaV2.2 both failed to co-precipitate the other protein. Further, while PDLIM5 was localized to the calyx terminal, quantitative analysis demonstrated that these two proteins do not co-localize or covary in this structure. Conclusion: We conclude that since PDLIM5 neither binds to, nor colocalizes with CaV2.2 it can not serve as a scaffold to link calcium channel accessory proteins.
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