Abstract
Mon1a was originally identified as a modifier gene of vesicular traffic, as a mutant Mon1a allele resulted in increased localization of cell surface proteins, whereas reduced levels of Mon1a showed decreased secretory activity. Here we show that Mon1a affects different steps in the secretory pathway including endoplasmic reticulum-to-Golgi traffic. siRNA-dependent reduction of Mon1a levels resulted in a delay in the reformation of the Golgi apparatus after Brefeldin A treatment. Endoglycosidase H treatment of ts045VSVG-GFP confirmed that knockdown of Mon1a delayed endoplasmic reticulum-to-Golgi trafficking. Reductions in Mon1a also resulted in delayed trafficking from Golgi to the plasma membrane. Immunoprecipitation and mass spectrometry analysis showed that Mon1a associates with dynein intermediate chain. Reductions in Mon1a or dynein altered steady state Golgi morphology. Reductions in Mon1a delayed formation of ERGIC-53-positive vesicles, whereas reductions in dynein did not affect vesicle formation. These data provide strong evidence for a role for Mon1a in anterograde trafficking through the secretory apparatus.
Highlights
Mon1a is known to be involved in membrane trafficking
We determined that Mon1a and Mon1b did not complement the loss of MON1 or CCZ1 in S. cerevisiae based upon vacuole morphology, growth on
We determined that reductions in Mon1a delay the reformation of the Golgi apparatus after brefeldin A (BFA) disruption and that Mon1a functions in efficient movement of molecules
Summary
Results: Reductions in Mon1a delay ER-to-Golgi trafficking and ERGIC-53-positive vesicle formation. Conclusion: Mon1a plays a role in anterograde trafficking in the secretory pathway. Reductions in Mon1a resulted in delayed trafficking from Golgi to the plasma membrane. Reductions in Mon1a delayed formation of ERGIC-53-positive vesicles, whereas reductions in dynein did not affect vesicle formation These data provide strong evidence for a role for Mon1a in anterograde trafficking through the secretory apparatus. A missense mutation in the Mon1a gene in C57BL/6 mice gives rise to a single amino acid substitution (N374S) at an evolutionarily conserved residue This substitution results in a “gain-of-function” allele causing an increase in the trafficking of membrane and soluble molecules through the biosynthetic pathway and increased localization of proteins at the plasma membrane. We show that Mon1a interacts with cytoplasmic dynein and provide evidence that both are required for efficient anterograde trafficking from ER to Golgi
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