Syntaxin 17, an ancient SNARE paralog, plays different and conserved roles in different organisms

Area of Science:

• Cell Biology
• Evolutionary Biology
• Molecular Biology

Background:

• Mammalian syntaxin 17 (Stx17) is involved in membrane fusion, mitochondrial division, and autophagosome formation.
• Stx17 possesses a unique C-terminal hydrophobic region and tail, distinguishing it from conventional syntaxins.
• Stx17 is an ancient SNARE protein found across eukaryotes but has been lost in some lineages.

Purpose of the Study:

• To compare the localization and function of fly and nematode Stx17 in HeLa cells against human Stx17.
• To investigate the evolutionary divergence of Stx17 functions in metazoans.

Main Methods:

• Expression of fly and nematode Stx17 in HeLa cells.
• Localization studies of Stx17 proteins.
• Functional assays for autophagy and mitochondrial division.

Main Results:

• Fly Stx17 localized to the cytosol, mediating autophagy but not mitochondrial division.
• Nematode Stx17 localized to mitochondria, facilitating mitochondrial division but not autophagy.
• Differences in Stx17 function correlate with variations in their C-terminal tail structures.

Conclusions:

• Stx17 has evolved distinct roles in autophagy and mitochondrial division across different metazoan lineages.
• The C-terminal tail structure of Stx17 is a key determinant of its functional specialization.
• This study offers insights into the evolutionary trajectory of Stx17 in metazoans.