Sjoegren syndrome nuclear autoantigen 1 (SSNA1/NA14) is a major specific target for autoantibodies in Sjögren's Syndrome, a highly prevalent autoimmune disease [, ]. SSNA1 is a microtubule-binding protein which stabilizes dynamic microtubules by slowing growth and shrinkage at both plus and minus ends and serves as a sensor of microtubule damage, protecting microtubules from the microtubule-severing enzyme SPAST []. SSNA1 can assemble into large fibrils, a structure that is important for its interaction with spastin as well as for microtubule dynamics []. It is also a binding partner for the G-protein coupled receptor TPRA40, which regulates early mouse embryogenesis []. Orthologues of SSNA1 are absent from the common eukaryotic model systems Saccharomyces cerevisiae, Caenorhabditis elegans and Drosophila melanogaster but are encoded by the genomes of the flagellated green alga Chlamydomonas reinhardtii (where it is known as deflagellation-inducible protein of 13kDa, DIP13), trematode worms and protozoan parasites. Chlamydomonas reinhardtii DIP13 is localised to centrioles, flagella and cytoplasmic microtubules. It is involved in cell division and flagellar assembly [, ].
