The origin and evolution of synaptic proteins - choanoflagellates lead the way.

The origin of neurons was a key event in evolution, allowing metazoans to evolve rapid behavioral responses to environmental cues. Reconstructing the origin of synaptic proteins promises to reveal their ancestral functions and might shed light on the evolution of the first neuron-like cells in metazoans. By analyzing the genomes of diverse metazoans and their closest relatives, the evolutionary history of diverse presynaptic and postsynaptic proteins has been reconstructed. These analyses revealed that choanoflagellates, the closest relatives of metazoans, possess diverse synaptic protein homologs. Recent studies have now begun to investigate their ancestral functions. A primordial neurosecretory apparatus in choanoflagellates was identified and it was found that the mechanism, by which presynaptic proteins required for secretion of neurotransmitters interact, is conserved in choanoflagellates and metazoans. Moreover, studies on the postsynaptic protein homolog Homer revealed unexpected localization patterns in choanoflagellates and new binding partners, both which are conserved in metazoans. These findings demonstrate that the study of choanoflagellates can uncover ancient and previously undescribed functions of synaptic proteins.

Two-hybrid analysis of the interaction between the fission yeast proteins Sal3 and Cdc25

Cdc25 is a mitosis triggering phosphatase in Schizosaccharomyces pombe, and is transported in to the nucleus during G2 phase by the importin-β protein Sal3. Cdc25 triggers mitosis and cell division by dephosphorylating tyrosine 15 of Cdc2. In sal3 mutants, Cdc25 is not transported into the nucleus and the cells halt in G2. The purpose of this study is to use a two-hybrid system to determine the nature of the relationship between Sal3 and Cdc25. Previous research has failed to detect any interaction between the two proteins, but specific modifications were made to the two-hybrid system in this study including the separation of Sal3 into its two binding domains, the addition of fluorescent tags to the fusion protein, and the reversal of plasmids in the fusion proteins. Unique PCR primers were successfully designed, based on a multiple alignment of Sal3 and its homologues, to separate Sal3 into its two domains.