A survey of the binding of polycationic ferritin in several fenestrated capillary beds: Indication of heterogeneity in the luminal glycocalyx of fenestral diaphragms

Bankston, Patrick W.; Milici, Anthony J.

doi:10.1016/0026-2862(83)90053-5

Cited by 59 publications

(22 citation statements)

References 13 publications

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“…Our study does not rule out the possibility that fenestrae in glomerular endothelial cells differ from those in other fenestrated endothelia. In fact, studies with cationic markers have long suggested that the composition of endothelial fenestral diaphragms differ in different organ beds (25). Also, the observation that the caveolar diaphragm protein PV-1 localizes to peritubular fenestral diaphragms but not glomerular fenestrae is consistent with the view that the molecular composition of bridging diaphragms differs between renal peritubular and glomerular fenestrae or that glomerular endothelial fenestrae do not contain bridging diaphragms (9).…”

Section: Discussionsupporting

confidence: 71%

Glomerular Endothelial Fenestrae In Vivo Are Not Formed from Caveolae

Sörensson¹,

Fierlbeck²,

Heider³

et al. 2002

Journal of the American Society of Nephrology

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Abstract. Previous reports indicate that endothelial fenestrae in vitro can form by fusion of caveolae or caveolae-like vesicles. The principal aim of this study was to determine whether formation of glomerular endothelial cell fenestrae in vivo similarly involves caveolae and caveolin-1. Whereas caveolin-1 immunofluorescence was found around the circumference of human and mouse glomerular capillary loops, it co-localized only partially with the endothelium-specific lectin Ulex Europaeus I in human glomeruli, leaving portions of the endothelium devoid of caveolin-1. Immunogold electron microscopy, used to definitively localize caveolin-1 in glomeruli, showed that caveolin-1 was completely excluded from the fenestrated portion of the endothelium. Moreover, in caveolin-1-deficient mice, which cannot form caveolae, the ultrastructure of glomerular endothelial fenestrae appeared entirely normal. Interestingly, strong caveolin-1 immunogold labeling was observed in podocytes, where some caveolin-1 localized to filtration slits. Caveolin-1 co-immunoprecipitated with the podocyte slit diaphragm proteins nephrin and CD2AP, and dual immunofluorescence confirmed co-localization of caveolin-1 and nephrin. Nevertheless, in caveolin-1-deficient mice, podocyte ultrastructure appeared normal, and the podocyte proteins synaptopodin, nephrin, and podocin were expressed normally. In addition, blood urea nitrogen concentrations and urinary protein excretion in these mice were similar to those in wild-type mice. Thus, unlike caveolae formation, glomerular endothelial cell fenestrae formation in vivo does not require caveolin-1, ruling out the previous hypothesis that endothelial fenestrae represent fused caveolae, at least for glomerular endothelial cells. Localization of caveolin-1 to podocytes and their filtration slits is consistent with the view that the filtration slit plasma membrane represents a type of lipid raft microdomain.

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Section: Discussionsupporting

confidence: 71%

Glomerular Endothelial Fenestrae In Vivo Are Not Formed from Caveolae

Sörensson¹,

Fierlbeck²,

Heider³

et al. 2002

Journal of the American Society of Nephrology

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“…As noted above, the presence ofincreased permeance at the site ofepithelial denudation offers additional evidence for the importance of the epithelial cell in glomerular permselectivity. By contrast, glomerular endothelial cells have large fenestrae (< 600 A diameter) which cover up to one third of the capillary surface (26) and are lined by an anionic, sialic acid diaphragm which contains heparan sulfate proteoglycan (27). Although hinderance to macromolecular permeability at glomerular fenestrae has been noted with some electron microscopy tracer studies ( 15 ), in general they are not considered a primary site of size restriction because oftheir very large radii (600 A), but may be more important in charge selectivity.…”

Section: Discussionmentioning

confidence: 99%

Glomerular permeability barrier in the rat. Functional assessment by in vitro methods.

Daniels¹,

Deen²,

Mayer³

et al. 1993

J. Clin. Invest.

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The formation of glomerular ultrafiltrate is dependent on the prevailing hemodynamic forces within the glomerular microcirculation and the intrinsic properties of the filtration barrier. However, direct assessment of the permeability barrier is difficult with most available techniques. We used confocal microscopy to image l-,m thick optical cross-sections of isolated intact glomeruli and glomeruli denuded of cells and quantitated dextran (70,000 mol wt) diffusion from the capillary lumen. Dextran permeance was 11 times greater for the acellular filtration barrier than the intact peripheral capillary. Consideration of the basement membrane and cells as series resistors demonstrated that cells of the filtration barrier contribute 90% of the total resistance to macromolecular permeance. Using a different approach, dextran sieving coefficients for acellular glomeruli consolidated as a multilayer sheet in a filtration cell were similar to those for intact glomeruli in vivo at radii 30-36 A and -50 times greater at a dextran radius of 60 A. The presence of cells significantly reduced hydraulic permeability determined on consolidated intact or acellular glomeruli in an ultrafiltration cell with 50 mmHg applied pressure. The glomerular basement membrane does restrict macromolecular permeability but cells are important determinants of the overall macromolecular and hydraulic permeability of the glomerulus. (J. Clin. Invest. 1993. 92:929-936.)

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“…The molecular composition of the SDs and FDs has been investigated with "general" probes such as lectins (Simionescu et al, 1982a;Pino, 1986) and cationized ferritin (Simionescu et al, 1981a(Simionescu et al, , 1981b(Simionescu et al, , 1981b(Simionescu et al, , 1982bBankston and Milici, 1983), which demonstrated that SDs and FDs behave differently: the former bind lectins avidly and lack anionic sites, whereas the latter do not (Simionescu et al, 1982a) or poorly (Pino, 1986) bind lectins and have multiple anionic sites conferred by heparan sulfate proteoglycans (HSPGs; Simionescu et al, 1981a). The HSPGs are present only on the luminal side of fenestrae (Simionescu et al, 1982b;Rostgaard and Qvortrup, 1997).…”

Section: Introductionmentioning

confidence: 99%

PV1 Is a Key Structural Component for the Formation of the Stomatal and Fenestral Diaphragms

Stan

Tkachenko²,

Niesman

2004

MBoC

125

156

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PV1 is an endothelial-specific integral membrane glycoprotein associated with the stomatal diaphragms of caveolae, transendothelial channels, and vesiculo-vacuolar organelles and the diaphragms of endothelial fenestrae. Multiple PV1 homodimers are found within each stomatal and fenestral diaphragm. We investigated the function of PV1 within these diaphragms and their regulation and found that treatment of endothelial cells in culture with phorbol myristate acetate (PMA) led to upregulation of PV1. This correlated with de novo formation of stomatal diaphragms of caveolae and transendothelial channels as well as fenestrae upon PMA treatment. The newly formed diaphragms could be labeled with anti-PV1 antibodies. The upregulation of PV1 and formation of stomatal and fenestral diaphragms by PMA was endothelium specific and was the highest in microvascular endothelial cells compared with their large vessel counterparts. By using a siRNA approach, PV1 mRNA silencing prevented the de novo formation of the diaphragms of caveolae as well as fenestrae and transendothelial channels. Overexpression of PV1 in endothelial cells as well as in cell types that do not harbor caveolar diaphragms in situ induced de novo formation of caveolar stomatal diaphragms. Lastly, PV1 upregulation by PMA required the activation of Erk1/2 MAP kinase pathway and was protein kinase C independent. Taken together, these data show that PV1 is a key structural component, necessary for the biogenesis of the stomatal and fenestral diaphragms.

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A survey of the binding of polycationic ferritin in several fenestrated capillary beds: Indication of heterogeneity in the luminal glycocalyx of fenestral diaphragms

Cited by 59 publications

References 13 publications

Glomerular Endothelial Fenestrae In Vivo Are Not Formed from Caveolae

Glomerular Endothelial Fenestrae In Vivo Are Not Formed from Caveolae

Glomerular permeability barrier in the rat. Functional assessment by in vitro methods.

PV1 Is a Key Structural Component for the Formation of the Stomatal and Fenestral Diaphragms

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