Limits...
The secreted plant N-glycoproteome and associated secretory pathways.

Ruiz-May E, Kim SJ, Brandizzi F, Rose JK - Front Plant Sci (2012)

Bottom Line: Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway.However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall.In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Cornell University Ithaca, NY, USA.

ABSTRACT
N-Glycosylation is a common form of eukaryotic protein post-translational modification, and one that is particularly prevalent in plant cell wall proteins. Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway. While there have been numerous studies of mammalian and yeast N-glycoproteins, less is known about the population complexity, biosynthesis, structural variation, and trafficking of their plant counterparts. However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall. In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.

No MeSH data available.


Related in: MedlinePlus

Representation of the secretory pathway followed by the N-glycoproteins. The biosynthesis of the N-glycans is initiated on the cytosolic face of the ER. The resulting Man5GlcNAc-PP-Dol precursor is then flipped onto the luminal side ER lumen where further maturation of the sugar precursor occurs (Glc3Man9GlcNAc-PP-Dol). At this point the N-glycan structure is transferred to the nascent polypeptide. After removal of three Glc residues the N-glycoproteins enter the calnexin-calreticulin cycle (CNX/CRT; Hebert et al., 1995). The alternate action of glucosidase II and UDP-glucose:glycoprotein glucosyltransferase drives the glycoprotein through this cycle until it is correctly folded and exported from the ER to the GA. Misfolded proteins are directed from the ER to the cytosol by the ER-associated degradation (ERAD) machinery for proteasomal hydrolysis (Hebert et al., 1995; Crofts et al., 1998; Helenius and Aebi, 2004; Jin et al., 2007; Lederkremer, 2009). Glucosyl transferase and glucosidases implicated the in the sugar trimming in the ER and identified in plants so far, are enlisted in Table 1. Subsequent modifications of the N-glycans occur in the GA and potentially in other cellular compartments, such as the chloroplast and vacuole (based on a model presented in Gomord et al. (2010). The first indirect insights into the location and orientation of plant glycosyltransferases were provided by immunolocalization of the enzyme products (Laine et al., 1991; Fitchette et al., 1994, 1999). Such studies indicated that β-1,2-xylose is added to plant N-glycans mainly in the medial Golgi while the α-1,3-fucosylation occurs predominantly in the trans-Golgi (Fitchette et al., 1994).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3368311&req=5

Figure 1: Representation of the secretory pathway followed by the N-glycoproteins. The biosynthesis of the N-glycans is initiated on the cytosolic face of the ER. The resulting Man5GlcNAc-PP-Dol precursor is then flipped onto the luminal side ER lumen where further maturation of the sugar precursor occurs (Glc3Man9GlcNAc-PP-Dol). At this point the N-glycan structure is transferred to the nascent polypeptide. After removal of three Glc residues the N-glycoproteins enter the calnexin-calreticulin cycle (CNX/CRT; Hebert et al., 1995). The alternate action of glucosidase II and UDP-glucose:glycoprotein glucosyltransferase drives the glycoprotein through this cycle until it is correctly folded and exported from the ER to the GA. Misfolded proteins are directed from the ER to the cytosol by the ER-associated degradation (ERAD) machinery for proteasomal hydrolysis (Hebert et al., 1995; Crofts et al., 1998; Helenius and Aebi, 2004; Jin et al., 2007; Lederkremer, 2009). Glucosyl transferase and glucosidases implicated the in the sugar trimming in the ER and identified in plants so far, are enlisted in Table 1. Subsequent modifications of the N-glycans occur in the GA and potentially in other cellular compartments, such as the chloroplast and vacuole (based on a model presented in Gomord et al. (2010). The first indirect insights into the location and orientation of plant glycosyltransferases were provided by immunolocalization of the enzyme products (Laine et al., 1991; Fitchette et al., 1994, 1999). Such studies indicated that β-1,2-xylose is added to plant N-glycans mainly in the medial Golgi while the α-1,3-fucosylation occurs predominantly in the trans-Golgi (Fitchette et al., 1994).

Mentions: As with all eukaryotes, protein glycosylation in plants is initiated in the endoplasmic reticulum (ER). However, the biosynthesis of the N-glycan precursor begins on the cytosolic side of the ER (Figure 1; Table 1), starting with the transfer of N-acetylglucosamine-phosphate from soluble UDP-GlcNAc to the lipid membrane bound dolichyl monophosphate (Dol-P), forming N-acetylglucosamine-pyrophosphatidyldolichol (GlcNAc-PP-Dol). Dol-P is one of the rate-limiting factors in N-linked protein glycosylation in yeast and mammalian cells (Burda and Aebi, 1999; Jones et al., 2005) and while this is likely also to be the case in plants, it has not yet been demonstrated. However, mutational defects in the biosynthesis of Dol-P in Arabidopsis have been shown cause multiple physiological effects, such as impaired plasma membrane integrity resulting in electrolyte leakage, reduced cellular turgor and stomatal conductance, and increased drought resistance (Zhang et al., 2008). One GlcNAc and five mannose (Man) residues are subsequently transferred from UDP-GlcNAc, or GDP-Man, respectively, in a controlled, stepwise manner to GlcNAc-PP-Dol, producing the Man5GlcNAc2-PP-Dol branched heptasaccharide intermediate (Helenius and Aebi, 2002).


The secreted plant N-glycoproteome and associated secretory pathways.

Ruiz-May E, Kim SJ, Brandizzi F, Rose JK - Front Plant Sci (2012)

Representation of the secretory pathway followed by the N-glycoproteins. The biosynthesis of the N-glycans is initiated on the cytosolic face of the ER. The resulting Man5GlcNAc-PP-Dol precursor is then flipped onto the luminal side ER lumen where further maturation of the sugar precursor occurs (Glc3Man9GlcNAc-PP-Dol). At this point the N-glycan structure is transferred to the nascent polypeptide. After removal of three Glc residues the N-glycoproteins enter the calnexin-calreticulin cycle (CNX/CRT; Hebert et al., 1995). The alternate action of glucosidase II and UDP-glucose:glycoprotein glucosyltransferase drives the glycoprotein through this cycle until it is correctly folded and exported from the ER to the GA. Misfolded proteins are directed from the ER to the cytosol by the ER-associated degradation (ERAD) machinery for proteasomal hydrolysis (Hebert et al., 1995; Crofts et al., 1998; Helenius and Aebi, 2004; Jin et al., 2007; Lederkremer, 2009). Glucosyl transferase and glucosidases implicated the in the sugar trimming in the ER and identified in plants so far, are enlisted in Table 1. Subsequent modifications of the N-glycans occur in the GA and potentially in other cellular compartments, such as the chloroplast and vacuole (based on a model presented in Gomord et al. (2010). The first indirect insights into the location and orientation of plant glycosyltransferases were provided by immunolocalization of the enzyme products (Laine et al., 1991; Fitchette et al., 1994, 1999). Such studies indicated that β-1,2-xylose is added to plant N-glycans mainly in the medial Golgi while the α-1,3-fucosylation occurs predominantly in the trans-Golgi (Fitchette et al., 1994).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368311&req=5

Figure 1: Representation of the secretory pathway followed by the N-glycoproteins. The biosynthesis of the N-glycans is initiated on the cytosolic face of the ER. The resulting Man5GlcNAc-PP-Dol precursor is then flipped onto the luminal side ER lumen where further maturation of the sugar precursor occurs (Glc3Man9GlcNAc-PP-Dol). At this point the N-glycan structure is transferred to the nascent polypeptide. After removal of three Glc residues the N-glycoproteins enter the calnexin-calreticulin cycle (CNX/CRT; Hebert et al., 1995). The alternate action of glucosidase II and UDP-glucose:glycoprotein glucosyltransferase drives the glycoprotein through this cycle until it is correctly folded and exported from the ER to the GA. Misfolded proteins are directed from the ER to the cytosol by the ER-associated degradation (ERAD) machinery for proteasomal hydrolysis (Hebert et al., 1995; Crofts et al., 1998; Helenius and Aebi, 2004; Jin et al., 2007; Lederkremer, 2009). Glucosyl transferase and glucosidases implicated the in the sugar trimming in the ER and identified in plants so far, are enlisted in Table 1. Subsequent modifications of the N-glycans occur in the GA and potentially in other cellular compartments, such as the chloroplast and vacuole (based on a model presented in Gomord et al. (2010). The first indirect insights into the location and orientation of plant glycosyltransferases were provided by immunolocalization of the enzyme products (Laine et al., 1991; Fitchette et al., 1994, 1999). Such studies indicated that β-1,2-xylose is added to plant N-glycans mainly in the medial Golgi while the α-1,3-fucosylation occurs predominantly in the trans-Golgi (Fitchette et al., 1994).
Mentions: As with all eukaryotes, protein glycosylation in plants is initiated in the endoplasmic reticulum (ER). However, the biosynthesis of the N-glycan precursor begins on the cytosolic side of the ER (Figure 1; Table 1), starting with the transfer of N-acetylglucosamine-phosphate from soluble UDP-GlcNAc to the lipid membrane bound dolichyl monophosphate (Dol-P), forming N-acetylglucosamine-pyrophosphatidyldolichol (GlcNAc-PP-Dol). Dol-P is one of the rate-limiting factors in N-linked protein glycosylation in yeast and mammalian cells (Burda and Aebi, 1999; Jones et al., 2005) and while this is likely also to be the case in plants, it has not yet been demonstrated. However, mutational defects in the biosynthesis of Dol-P in Arabidopsis have been shown cause multiple physiological effects, such as impaired plasma membrane integrity resulting in electrolyte leakage, reduced cellular turgor and stomatal conductance, and increased drought resistance (Zhang et al., 2008). One GlcNAc and five mannose (Man) residues are subsequently transferred from UDP-GlcNAc, or GDP-Man, respectively, in a controlled, stepwise manner to GlcNAc-PP-Dol, producing the Man5GlcNAc2-PP-Dol branched heptasaccharide intermediate (Helenius and Aebi, 2002).

Bottom Line: Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway.However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall.In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Cornell University Ithaca, NY, USA.

ABSTRACT
N-Glycosylation is a common form of eukaryotic protein post-translational modification, and one that is particularly prevalent in plant cell wall proteins. Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway. While there have been numerous studies of mammalian and yeast N-glycoproteins, less is known about the population complexity, biosynthesis, structural variation, and trafficking of their plant counterparts. However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall. In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.

No MeSH data available.


Related in: MedlinePlus