The role of early-Golgi N-glycosylation enzyme complexes
Abstract
The Golgi apparatus is the central biosynthetic organelle of the secretory pathway and as such plays a pivotal role in the transport and concomitant modification of proteins and polysaccharides in all eukaryotes. The step-wise modification of protein-bound asparagine-linked oligosaccharides (N-glycans) in the stacks of the plant Golgi apparatus is the outcome of multiple sequentially acting glycosidases and glycosyltransferases, which are asymmetrically distributed across the cis-, medial- and trans-Golgi cisternae. It is commonly believed that the highly-defined cisternal organisation of Golgi-resident enzymes is necessary and essential for the functionality of the Golgi. How this asymmetric Golgi distribution is established and maintained is currently unknown and the mechanisms that regulate Golgi enzyme organisation and interaction with cargo molecules are not understood. By using the non-invasive biophysical FRET-FLIM method we recently discovered that several cis/medial-Golgi enzymes involved in N-glycan processing assemble into homo- and heterodimeric complexes in planta. We hypothesise that the assembly of discrete subsets of enzymes into functionally relevant enzyme complexes via protein-protein interactions could serve to maintain the compartment-specific Golgi (protein) organisation and/or may be a functional tool to regulate N-glycan processing. So far the biological significance of enzyme complex formation in the plant Golgi is speculative and it is also not clear whether the existing homo- and heterodimers are part of a larger oligomeric enzyme complex. This project aims to characterise an N-glycan processing enzyme complex that resides in the cis/medial-cisternae of plant Golgi stacks. We will utilise complementary cell biological, genetic, biochemical and proteomics approaches to identify its biological role in the development and physiology of plants and unravel its functional relevance in the maintenance of normal Golgi functions such as the specific protein glycosylation events in plant cells. To investigate the potential formation of a multi-enzyme complex in planta we will develop and apply 3-colour FRET combined multiphoton-induced FLIM to visualise multiple interactions at the same time in the same organelle. Together, these experiments will elucidate the composition and the biological significance of the identified enzyme complex and provide novel insights into the organisation of the plant Golgi apparatus and its resident proteins at a structural and functional level.
Publikationen
Project staff
Jennifer Schoberer
Mag. Dr. Jennifer Schoberer
jennifer.schoberer@boku.ac.at
Tel: +43 1 47654-94346
Project Leader
01.02.2014 - 31.01.2019