Struthers, Marion Symington
An evolutionarily conserved regulatory mechanism for endosomal membrane trafficking.
PhD thesis, University of Glasgow.
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Membrane fusion in all eukaryotic cells is facilitated by the formation of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes; a process that is regulated by Sec1p/Munc18 (SM) proteins. Membrane fusion has been conserved through evolution and hence a lot or our knowledge about the molecular mechanism that regulates membrane traffic has come from experimentally tractable model organisms such as Saccharomyces cerevisiae. The work presented in this thesis demonstrates that the mammalian SNARE protein, syntaxin 16 (Sx16), is a functional homologue of the yeast SNARE protein, Tlg2p, as expression of Sx16 in tlg2Δ cells, fully complements trafficking defects displayed by these cells. This finding is supported by experiments demonstrating that Sx16 interacts both physically and functionally with the SM protein of Tlg2p, Vps45p, both in vivo and in vitro. Vps45p regulates Sx16 in a manner similar to the way that it regulates Tlg2p; controlling entry into functional SNARE complexes and regulating cellular levels. A model, in which Vps45p is required for regulating membrane fusion and regulating the cellular levels of Tlg2p, is also presented and discussed in this thesis.
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