Involvement of thapsigargin and cyclopiazonic acid–sensitive pumps in the rescue of TMEM165-associated glycosylation defects by Mn2+

Congenital disorders of glycosylation are severe inherited diseases in which aberrant protein glycosylation is a hallmark. Transmembrane protein 165 (TMEM165) is a novel Golgi transmembrane protein involved in type II congenital disorders of glycosylation. Although its biologic function is still a controversial issue, we have demonstrated that the Golgi glycosylation defect due to TMEM165 deficiency resulted from a Golgi Mn2+ homeostasis defect. The goal of this study was to delineate the cellular pathway by which extracellular Mn2+ rescues N-glycosylation in TMEM165 knockout (KO) cells. We first demonstrated that after extracellular exposure, Mn2+ uptake by HEK293 cells at the plasma membrane did not rely on endocytosis but was likely done by plasma membrane transporters. Second, we showed that the secretory pathway Ca2+-ATPase 1, also known to mediate the influx of cytosolic Mn2+ into the lumen of the Golgi apparatus, is not crucial for the Mn2+-induced rescue glycosylation of lysosomal-associated membr...