The Golgi alpha-1,6 mannosyltransferase KlOch1p of Kluyveromyces lactis is required for Ca2+/calmodulin-based signaling and for proper mitochondrial functionality.
BACKGROUND
Protein N-glycosylation is a relevant metabolic pathway in eukaryotes and plays key roles in cell processes. In yeasts, outer chain branching is initiated in the Golgi apparatus by the alpha-1,6-mannosyltransferase Och1p.


RESULTS
Here we report that, in Kluyveromyces lactis, this glycosyltransferase is also required to maintain functional mitochondria and calcium homeostasis. Cells carrying a mutation in KlOCH1 gene showed altered mitochondrial morphology, increased accumulation of ROS and reduced expression of calcium signalling genes such as calmodulin and calcineurin. Intracellular calcium concentration was also reduced in the mutant cells with respect to the wild type counterparts.Phenotypes that occur in cells lacking the alpha-1,6-mannosyltransferase, including oxidative stress and impaired mitochondria functionality, were suppressed by increased dosage of KlCmd1p. This, in turn, acts through the action of calcineurin.


CONCLUSIONS
Proper functioning of the alpha-1,6-mannosyltransferase in the N-glycosylation pathway of K. lactis is required for maintaining normal calcium homeostasis; this is necessary for physiological mitochondria dynamics and functionality.
Zanni
Elena
E
Dpt, Developmental and Cell Biology, University LA SAPIENZA, P.le. A. Moro, 500185 Rome, Italy.
Farina
Francesca
F
Ricci
Antonella
A
Mancini
Patrizia
P
Frank
Claudio
C
Palleschi
Claudio
C
Uccelletti
Daniela
D
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002147:Calmodulin / Q000378:metabolism*; D006056:Golgi Apparatus / Q000201:enzymology; D006706:Homeostasis; D007716:Kluyveromyces / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D018384:Oxidative Stress
D002147:Calmodulin; D008364:Mannosyltransferases; D002118:Calcium