Involvement of Thapsigargin- and Cyclopiazonic Acid-sensitive Pumps in the Rescue of TMEM165-associated Glycosylation Defects by Mn

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 Mn homeostasis defect. The goal of this study was to delineate the cellular pathway by which extracellular Mn rescues N-glycosylation in TMEM165 knockout (KO) cells. We first demonstrated that after extracellular exposure, Mn 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 Ca-ATPase 1, also known to mediate the influx of cytosolic Mn into the lumen of the Golgi apparatus, is not crucial for the Mn-induced rescue glycosylation of lysosomal-associated membrane protein 2 (LAMP2). In contrast, our results demonstrate the involvement of cyclopiazonic acid- and thapsigargin (Tg)-sensitive pumps in the rescue of TMEM165-associated glycosylation defects by Mn. Interestingly, overexpression of sarco/endoplasmic reticulum Ca-ATPase (SERCA) 2b isoform in TMEM165 KO cells partially rescues the observed LAMP2 glycosylation defect. Overall, this study indicates that the rescue of Golgi N-glycosylation defects in TMEM165 KO cells by extracellular Mn involves the activity of Tg and cyclopiazonic acid-sensitive pumps, probably the SERCA pumps.-Houdou, M., Lebredonchel, E., Garat, A., Duvet, S., Legrand, D., Decool, V., Klein, A., Ouzzine, M., Gasnier, B., Potelle, S., Foulquier, F. Involvement of thapsigargin- and cyclopiazonic acid-sensitive pumps in the rescue of TMEM165-associated glycosylation defects by Mn.