The role of protein phosphorylation in α2,6(N)-sialyltransferase activity

Breen, Kieran C.; Georgopoulou, Niki

doi:10.1016/s0006-291x(03)01529-8

Cited by 6 publications

(6 citation statements)

References 18 publications

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“…Therefore, activation of PKC pathway can promote both UT-A1 and UT-A3 sialylation. This is consistent with a study by Breen et al showing that stimulation of PKC resulted in an increase in ST6GalI catalytic activity (5). Ma et al reported the presence of phosphorylated serine and threonine sites on α2, 6-sialyltransferase (12), suggesting a functional involvement of ST6GalI-mediated sialylation by PKC activation.…”

Section: Discussionsupporting

confidence: 93%

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Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation

Qian

Sands

Song

et al. 2016

Pflugers Arch - Eur J Physiol

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Two urea transporters, UT-A1 and UT-A3, are expressed in the kidney terminal inner medullary collecting duct (IMCD) and are important for the production of concentrated urine. UT-A1, as the largest isoform of all UT-A urea transporters, has gained much attention and been extensively studied; however the role and the regulation of UT-A3 are less explored. In this study, we investigated UT-A3 regulation by glycosylation modification. A site-directed mutagenesis verified a single glycosylation site in UT-A3 at Asn279. Loss of the glycosylation reduced forskolin-stimulated UT-A3 cell membrane expression and urea transport activity. UT-A3 has two glycosylation forms, 45 kDa and 65 kDa. Using sugar specific-binding lectins, the UT-A3 glycosylation profile was examined. The 45 kDa form was pulled down by lectin Con A and GNL, indicating an immature glycan with a high amount of mannose (Man); whereas the 65 kDa form is a mature glycan composed of acetylglucosamine (GlcNAc), poly-N-acetyllactosame (poly-LacNAc) that was pulled down by WGA and tomato lectin, respectively. Interestingly, the mature form of UT-A3 glycan contains significant amounts of sialic acid. We explored the enzymes responsible for directing UT-A3 sialylation. Sialyltransferase ST6GalI, but not ST3GalIV, catabolizes UT-A3 α2, 6-sialylation. Activation of PKC by PDB treatment promoted UT-A3 glycan sialylation and membrane surface expression. PKC inhibitor chelerythrine blocks ST6GalI-induced UT-A3 sialylation. Increased sialylation by ST6GalI increased UT-A3 protein stability and urea transport activity. Collectively, our study reveals a novel mechanism of UT-A3 regulation by ST6GalI-mediated sialylation modification that may play an important in kidney urea reabsorption and the urinary concentrating mechanism.

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Section: Discussionsupporting

confidence: 93%

“…Lipid raft fractions (2-5) were collected for lectin pull-down assay and followed by Western blot with antibodies to UT-A1 NH 2 -terminus. A representative blot was shown from >3 different experiments.…”

Section: Figurementioning

confidence: 99%

Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation

Qian

Sands

Song

et al. 2016

Pflugers Arch - Eur J Physiol

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“…For example, treatment of NRK cells with activators of protein kinase A alters vesicular stomatitis virus G protein glycosylation in infected cells (Muniz et al, 1996;Muniz et al, 1997). Furthermore, protein kinase C activity modulates sialylation of glycosphingolipids in NG108-15 and of glycoproteins in SH-SY5Y, as well as polysialylation of NCAM in neuro-2A and PC-12 cells (Bieberich et al, 1998;Breen and Georgopoulou, 2003;Gallagher et al, 2000). However, the functional consequences of these pharmacological effects have not been validated in vivo, nor have molecular or cellular mechanisms underlying altered glycosylation been identified.…”

Section: Tissue-specific Protein Glycosylation Requires Coordinated Tmentioning

confidence: 99%

Sugar-free frosting, a homolog of SAD kinase, drives neural-specific glycan expression in the Drosophila embryo

et al. 2011

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SUMMARYPrecise glycan structures on specific glycoproteins impart functionalities essential for neural development. However, mechanisms controlling embryonic neural-specific glycosylation are unknown. A genetic screen for relevant mutations in Drosophila generated the sugar-free frosting (sff) mutant that reveals a new function for protein kinases in regulating substrate flux through specific Golgi processing pathways. Sff is the Drosophila homolog of SAD kinase, which regulates synaptic vesicle tethering and neuronal polarity in nematodes and vertebrates. Our Drosophila sff mutant phenotype has features in common with SAD kinase mutant phenotypes in these other organisms, but we detect altered neural glycosylation well before the initiation of embryonic synaptogenesis. Characterization of Golgi compartmentation markers indicates altered colocalization that is consistent with the detected shift in glycan complexity in sff mutant embryos. Therefore, in analogy to synaptic vesicle tethering, we propose that Sff regulates vesicle tethering at Golgi membranes in the developing Drosophila embryo. Furthermore, neuronal sff expression is dependent on transcellular signaling through a non-neural toll-like receptor, linking neural-specific glycan expression to a kinase activity that is induced in response to environmental cues.

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“…The proposed involvement of PKC in the regulation of PST-mediated NCAM polysialylation state stems from the observation that phorbol-12-myristate-13-acetate, which activates diacylglycerol-dependent PKC isoforms, induces a dose-dependent decrease in NCAM PSA expression in neuro-2A neuroblastoma cells and staurosporine, a pan-specific PKC inhibitor, increases NCAM polysialylation state [26] Moreover, immunoblotting procedures have demonstrated reduced PKC expression to be associated with the enhanced polysialylation of NCAM in vitro and, using a polyclonal antibody directed against a conserved 11-amino acid sequence in E. coli polysialyltransferase, hippocampal PKC has been found to form complexes with PST that increase as animals age [27] and NCAM PSA expression decreases in an exponential manner [28]. The PST associated with these complexes has also been observed to be phosphorylated on serine residues [27], a mechanism known to be associated with the inhibition of other sialyltransferases [29], [30], [31] and [32]. Phosphorylated tyrosine residues on PST are also found in PST:PKC immunocomplexes [27] and this may play a crucial role in regulating PKC expression as phosphorylation of conserved tyrosine residues in the hinged bilobal structure, typical of the PKC family of isozymes, confers a specific post-translational control on the rate of proteolytic cleavage [33] and [34].…”

Section: Introductionmentioning

confidence: 99%

Curcumin-induced degradation of PKCδ is associated with enhanced dentate NCAM PSA expression and spatial learning in adult and aged Wistar rats

Conboy

Foley

O’Boyle

et al. 2009

Biochemical Pharmacology

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Polysialylation of the neural cell adhesion molecule (NCAM PSA) is necessary for the consolidation processes of hippocampus-based learning. Previously, we have found inhibition of protein kinase C delta (PKCdelta) to be associated with increased polysialyltransferase (PST) activity, suggesting inhibitors of this kinase might ameliorate cognitive deficits. Using a rottlerin template, a drug previously considered an inhibitor of PKCdelta, we searched the Compounds Available for Purchase (CAP) database with the Accelrys((R)) Catalyst programme for structurally similar molecules and, using the available crystal structure of the phorbol-binding domain of PKCdelta, found that diferuloylmethane (curcumin) docked effectively into the phorbol site. Curcumin increased NCAM PSA expression in cultured neuro-2A neuroblastoma cells and this was inversely related to PKCdelta protein expression. Curcumin did not directly inhibit PKCdelta activity but formed a tight complex with the enzyme. With increasing doses of curcumin, the Tyr(131) residue of PKCdelta, which is known to direct its degradation, became progressively phosphorylated and this was associated with numerous Tyr(131)-phospho-PKCdelta fragments. Chronic administration of curcumin in vivo also increased the frequency of polysialylated cells in the dentate infragranular zone and significantly improved the acquisition and consolidation of a water maze spatial learning paradigm in both adult and aged cohorts of Wistar rats. These results further confirm the role of PKCdelta in regulating PST and NCAM PSA expression and provide evidence that drug modulation of this system enhances the process of memory consolidation.

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The role of protein phosphorylation in α2,6(N)-sialyltransferase activity

Cited by 6 publications

References 18 publications

Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation

Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation

Sugar-free frosting, a homolog of SAD kinase, drives neural-specific glycan expression in the Drosophila embryo

Curcumin-induced degradation of PKCδ is associated with enhanced dentate NCAM PSA expression and spatial learning in adult and aged Wistar rats

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