Vacuolar sorting receptors (VSRs) in Arabidopsis mediate the sorting of soluble proteins to vacuoles in the secretory pathway. The VSRs are post-translationally modified by the attachment of N-glycans, but the functional significance of such a modification remains unknown. Here we have studied the role(s) of glycosylation in the stability, trafficking and vacuolar protein transport of AtVSR1 in Arabidopsis protoplasts. AtVSR1 harbors three complex-type N-glycans, which are located in the N-terminal 'PA domain', the central region and the C-terminal epidermal growth factor repeat domain, respectively. We have demonstrated that: (i) the N-glycans do not affect the targeting of AtVSR1 to pre-vacuolar compartments (PVCs) and its vacuolar degradation; and (ii) N-glycosylation alters the binding affinity of AtVSR1 to cargo proteins and affects the transport of cargo into the vacuole. Hence, N-glycosylation of AtVSR1 plays a critical role in its function as a VSR in plants.
Keywords: Arabidopsis; N-glycosylation; cargo; vacuolar protein; vacuolar sorting receptor.
© 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.