A novel tripartite motif involved in aquaporin topogenesis, monomer folding and tetramerization

Buck, Teresa M.; Wagner, J.R.; Grund, Steven; Skach, William R.

doi:10.1038/nsmb1275

Cited by 63 publications

(77 citation statements)

References 50 publications

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“…Interestingly, AQP1 proved to be the most sensitive substrate for perturbations of OST-mediated protein N-glycosylation using our in vitro assay. This most likely reflects the fact that the glycosylation of Asn-42 of AQP1 is complex, and relies on the initial translocation of TM2 into the ER lumen prior to the subsequent topological maturation of the precursor into its final structure (Buck et al, 2007;Foster et al, 2000). Our studies of protein N-glycosylation using a cell-based system bear out this model.…”

Section: Discussionmentioning

confidence: 89%

The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation

Roboti

High

2012

Journal of Cell Science

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SummaryProtein N-glycosylation is an essential modification that occurs in all eukaryotes and is catalysed by the oligosaccharyltransferase (OST) in the endoplasmic reticulum. Comparative studies have clearly shown that eukaryotic STT3 proteins alone can fulfil the enzymatic requirements for N-glycosylation, yet in many cases STT3 homologues form stable complexes with a variety of non-catalytic OST subunits. Whereas some of these additional components might play a structural role, others appear to increase or modulate Nglycosylation efficiency for certain precursors. Here, we have analysed the roles of three non-catalytic mammalian OST components by studying the consequences of subunit-specific knockdowns on the stability and enzymatic activity of the OST complex. Our results demonstrate that OST48 and DAD1 are required for the assembly of both STT3A-and STT3B-containing OST complexes. The structural perturbations of these complexes we observe in OST48-and DAD1-depleted cells underlie their pronounced hypoglycosylation phenotypes. Thus, OST48 and DAD1 are global modulators of OST stability and hence N-glycosylation. We show that KCP2 also influences protein N-glycosylation, yet in this case, the effect of its depletion is substrate specific, and is characterised by the accumulation of a novel STT3A-containing OST subcomplex. Our results suggest that KCP2 acts to selectively enhance the OST-dependent processing of specific protein precursors, most likely co-translational substrates of STT3A-containing complexes, highlighting the potential for increased complexity of OST subunit composition in higher eukaryotes.

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Section: Discussionmentioning

confidence: 89%

The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation

Roboti

High

2012

Journal of Cell Science

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“…Furthermore the N-and C-terminal domains of AQP1 are thought to be involved in its tetramer formation (2-4, 20, 21). Recently, it has also been reported that although the residues are unique to AQP1, Lys 51 of TM2 interacts with Asp 185 of TM5 on an adjacent monomer to stabilize the AQP1 tetramer (22). Because the degree of amino acid sequence similarity between AQP11 and other AQPs is rather low, it is difficult to predict the three-dimensional structure of AQP11 using homology modeling (7).…”

Section: Discussionmentioning

confidence: 99%

The NPC Motif of Aquaporin-11, Unlike the NPA Motif of Known Aquaporins, Is Essential for Full Expression of Molecular Function

Ikeda¹,

Andoo²,

Shimono³

et al. 2011

Journal of Biological Chemistry

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The recently identified molecule aquaporin-11 (AQP11) has a unique amino acid sequence pattern that includes an AsnPro-Cys (NPC) motif, corresponding to the N-terminal AsnPro-Ala (NPA) signature motif of conventional AQPs. In this study, we examined the effect of the mutation of the NPC motif on the subcellular localization, oligomerization, and water permeability of AQP11 in transfected mammalian cells. Furthermore, the effect was also assessed using zebrafish. Sitedirected mutation at the NPC motif did not affect the subcellular localization of AQP11 but reduced its oligomerization. A cell swelling assay revealed that cells expressing AQP11 with a mutated NPC motif had significantly lower osmotic water permeability than cells expressing wild-type AQP11. Zebrafish deficient in endogenous AQP11 showed a deformity in the tail region at an early stage of development. This phenotype was dramatically rescued by injection of human wild-type AQP11 mRNA, whereas the effect of mRNA for AQP11 with a mutated NPC motif was less marked. Although the NPA motif is known to be important for formation of water-permeable pores by conventional AQPs, our observations suggest that the corresponding NPC motif of AQP11 is essential for full expression of molecular function.

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“…Oligomer formation is the prerequisite for the function of several channels, receptors, and transporters. In particular, the tetramer formation of aquaporin is critical to its water permeability and ion selectivity (52)(53)(54), whereas each aquaporin subunit has a water channel in the center. We speculate that the interaction of dSPP/NT resulted in a conformational change of each subunit that affects the formation and/or the stability of the dSPP tetramer, thereby causing the dominant negative effect (Fig.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional Structure of the Signal Peptide Peptidase

Miyashita

Maruyama

Isshiki

et al. 2011

Journal of Biological Chemistry

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Signal peptide peptidase (SPP) is an atypical aspartic protease that hydrolyzes peptide bonds within the transmembrane domain of substrates and is implicated in several biological and pathological functions. Here, we analyzed the structure of human SPP by electron microscopy and reconstructed the three-dimensional structure at a resolution of 22 Å . Enzymatically active SPP forms a slender, bullet-shaped homotetramer with dimensions of 85 ؋ 85 ؋ 130 Å . The SPP complex has four concaves on the rhombus-like sides, connected to a large chamber inside the molecule. Intriguingly, the N-terminal region of SPP is sufficient for the tetrameric assembly. Moreover, overexpression of the N-terminal region inhibited the formation of the endogenous SPP tetramer and the proteolytic activity within cells. These data suggest that the homotetramer is the functional unit of SPP and that its N-terminal region, which works as the structural scaffold, has a novel modulatory function for the intramembrane-cleaving activity of SPP.The intramembrane-cleaving proteases (I-CLiPs) 5 that sever the transmembrane domains of their substrates have been identified in a range of organisms and play a variety of roles in

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A novel tripartite motif involved in aquaporin topogenesis, monomer folding and tetramerization

Cited by 63 publications

References 50 publications

The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation

The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation

The NPC Motif of Aquaporin-11, Unlike the NPA Motif of Known Aquaporins, Is Essential for Full Expression of Molecular Function

Three-dimensional Structure of the Signal Peptide Peptidase

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