title: RNAi knockdown of parafusin inhibits the secretory pathway.
abstract: Several glycolytic enzymes and their isoforms have been found to be important in cell signaling unrelated to glycolysis. The involvement of parafusin (PFUS), a member of the phosphoglucomutase (PGM) superfamily with no phosphoglucomutase activity, in Ca(2+)-dependent exocytosis has been controversial. This protein was first described in Paramecium tetraurelia, but is widely found. Earlier work showed that parafusin is a secretory vesicle scaffold component with unusual post-translational modifications (cyclic phosphorylation and phosphoglucosylation) coupled to stages in the exocytic process. Using RNAi, we demonstrate that parafusin synthesis can be reversibly blocked, with minor or no effect on other PGM isoforms. PFUS knockdown produces an inhibition of dense core secretory vesicle (DCSV) synthesis leading to an exo(-) phenotype. Although cell growth is unaffected, vesicle content is not packaged properly and no new DCSVs are formed. We conclude that PFUS and its orthologs are necessary for proper scaffold maturation. Because of this association, parafusin is an important signaling component for regulatory control of the secretory pathway.
authors.affiliation: Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Wyroba
authors.forename: Birgit H
authors.initials: BH
authors.lastname: Satir
mesh_terms: D040461:Gene Components; D055785:Gene Knockdown Techniques; D006019:Glycolysis; D047468:Immunoprecipitation; D016805:Paramecium tetraurelia / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010641:Phenotype; D010733:Phosphoglucomutase / Q000235:genetics* / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D015183:Restriction Mapping; D055571:Secretory Pathway; D022142:Secretory Vesicles / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D020033:Protein Isoforms; D015800:Protozoan Proteins; C087273:parafusin protein, Paramecium; D010733:Phosphoglucomutase