title: Alteration of ZnT5-mediated zinc import into the early secretory pathway affects the secretion of growth hormone from rat pituitary cells.
abstract: BACKGROUND
  Aggregation of growth hormone (GH) required for its proper storage in granules is facilitated by zinc (Zn(2+)) transported by specific zinc transporters in and out of the regulated secretory pathway. Slc30a5 (ZnT5) was reported to have the highest gene expression among all zinc transporters in primary mouse pituitary cells while ZnT5-null mice presented with abnormal bone development and impaired growth compared to wild-type counterparts.
  
  
  METHODS
  In vitro studies performed in GH3 cells, a rat pituitary cell line that endogenously produces rat GH (rGH), included analysis of: cytoplasmic Zn(2+) pool changes after altering rSlc30a5 expression (luciferase assay), rZnT5 association with different compartments of the regulated secretory pathway (confocal microscopy), and the rGH secretion after rSlc30a5 knock-down (Western blot).
  
  
  RESULTS
  Confocal microscopy demonstrated high co-localization of rZnT5 with ER and Golgi (early secretory pathway) while siRNA-mediated knock-down of rSlc30a5 gene expression led to a significant reduction in rGH secretion. Furthermore, altered expression of rSlc30a5 (knock-down/overexpression) evoked changes in the cytoplasmic Zn(2+) pool indicating its important role in mediating Zn(2+) influx into intracellular compartments of the regulated secretory pathway.
  
  
  CONCLUSIONS
  Taken together, these results suggest that ZnT5 might play an important role in regulated GH secretion that is much greater than previously anticipated.
authors.affiliation: Division of Pediatric Endocrinology, Diabetology and Metabolism and Department of Clinical Research, University Children's Hospital, Bern, Switzerland.
authors.forename: Vibor
authors.initials: V
authors.lastname: Petkovic
authors.forename: Maria Consolata
authors.initials: MC
authors.lastname: Miletta
authors.forename: Andrée
authors.initials: A
authors.lastname: Eblé
authors.forename: Christa E
authors.initials: CE
authors.lastname: Flück
authors.forename: Primus-E
authors.initials: PE
authors.lastname: Mullis
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics*; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D055785:Gene Knockdown Techniques; D013006:Growth Hormone / Q000378:metabolism*; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D055571:Secretory Pathway / Q000235:genetics*; D015032:Zinc / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D018076:DNA, Complementary; D034741:RNA, Small Interfering; C000591231:zinc transporter 5, rat; D013006:Growth Hormone; D015032:Zinc