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SDPR induces membrane curvature and functions in the formation of caveolae.

Hansen CG, Bright NA, Howard G, Nichols BJ - Nat. Cell Biol. (2009)

Bottom Line: Here we show that loss of SDPR (serum deprivation protein response) causes loss of caveolae.SDPR binds directly to PTRF and recruits PTRF to caveolar membranes.STB colocalizes extensively with both SDPR and caveolin 1.

View Article: PubMed Central - PubMed

Affiliation: MRC-LMB, Cambridge, UK.

ABSTRACT
Caveolae are plasma membrane invaginations with a characteristic flask-shaped morphology. They function in diverse cellular processes, including endocytosis. The mechanism by which caveolae are generated is not fully understood, but both caveolin proteins and PTRF (polymerase I and transcript release factor, also known as cavin) are important. Here we show that loss of SDPR (serum deprivation protein response) causes loss of caveolae. SDPR binds directly to PTRF and recruits PTRF to caveolar membranes. Overexpression of SDPR, unlike PTRF, induces deformation of caveolae and extensive tubulation of the plasma membrane. The B-subunit of Shiga toxin (STB) also induces membrane tubulation and these membrane tubes also originate from caveolae. STB colocalizes extensively with both SDPR and caveolin 1. Loss of caveolae reduces the propensity of STB to induce membrane tubulation. We conclude that SDPR is a membrane-curvature-inducing component of caveolae, and that STB-induced membrane tubulation is facilitated by caveolae.

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SDPR over-expression induces membrane tubes derived from caveolaeA. Labeling of HeLa cells, two of which are over-expressing SDPR-GFP, with fluorescent antibodies against the GPI-linked protein CD59. Live cells were labeled for 20min prior to imaging. The lower panels show a magnified view of the region denoted by the dashed line. Confocal images. Bar 20μm. B. Localization of caveolin 1 to the ends of SDPR-mCh positive membrane tubes. Caveolin 1 was detected with polyclonal antibodies using indirect immunofluorescence. Bar 10μm. The lower panels show further examples of SDPR-induced membrane tubes with caveolin 1 puncta at one end. All images are confocal. C. Different distribution of over-expressed SDPR mutants. Different GFP-tagged mutants of SDPR as indicated were over-expressed at similar levels in live HeLa cells and imaged by confocal microscopy. Bar 20μm. D. Mapping of the region of SDPR required for membrane targeting and tubulation. The diagram indicates a selected subset of all constructs analyzed, with a score representing their sub-cellular distribution based on up to 3 stars. Only over-expressing cells were analyzed - some mutants that are not membrane targeted when over-expressed are still found in caveolae when expressed at low levels, presumably because of binding to endogenous SDPR or another caveolar component. Construct 105-425 was occasionally observed in the nucleus as well as the cytosol.
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Figure 5: SDPR over-expression induces membrane tubes derived from caveolaeA. Labeling of HeLa cells, two of which are over-expressing SDPR-GFP, with fluorescent antibodies against the GPI-linked protein CD59. Live cells were labeled for 20min prior to imaging. The lower panels show a magnified view of the region denoted by the dashed line. Confocal images. Bar 20μm. B. Localization of caveolin 1 to the ends of SDPR-mCh positive membrane tubes. Caveolin 1 was detected with polyclonal antibodies using indirect immunofluorescence. Bar 10μm. The lower panels show further examples of SDPR-induced membrane tubes with caveolin 1 puncta at one end. All images are confocal. C. Different distribution of over-expressed SDPR mutants. Different GFP-tagged mutants of SDPR as indicated were over-expressed at similar levels in live HeLa cells and imaged by confocal microscopy. Bar 20μm. D. Mapping of the region of SDPR required for membrane targeting and tubulation. The diagram indicates a selected subset of all constructs analyzed, with a score representing their sub-cellular distribution based on up to 3 stars. Only over-expressing cells were analyzed - some mutants that are not membrane targeted when over-expressed are still found in caveolae when expressed at low levels, presumably because of binding to endogenous SDPR or another caveolar component. Construct 105-425 was occasionally observed in the nucleus as well as the cytosol.

Mentions: Over-expression of SDPR causes accumulation of pronounced tubes in both HeLa and cav1−/− MEF cells, suggesting that SDPR may be able to stablize or generate membrane curvature. Labeling of HeLa cells with fluorescent antibodies against the plasma membrane marker CD59 confirmed that the SDPR-positive tubes are composed of plasma membrane derived membrane, and that these tubes are induced by expression of SDPR as they were not observed in non-transfected cells (Figure 5A). Expression of un-tagged SDPR also resulted in extensive membrane tubulation (Supplementary Figure 5B).


SDPR induces membrane curvature and functions in the formation of caveolae.

Hansen CG, Bright NA, Howard G, Nichols BJ - Nat. Cell Biol. (2009)

SDPR over-expression induces membrane tubes derived from caveolaeA. Labeling of HeLa cells, two of which are over-expressing SDPR-GFP, with fluorescent antibodies against the GPI-linked protein CD59. Live cells were labeled for 20min prior to imaging. The lower panels show a magnified view of the region denoted by the dashed line. Confocal images. Bar 20μm. B. Localization of caveolin 1 to the ends of SDPR-mCh positive membrane tubes. Caveolin 1 was detected with polyclonal antibodies using indirect immunofluorescence. Bar 10μm. The lower panels show further examples of SDPR-induced membrane tubes with caveolin 1 puncta at one end. All images are confocal. C. Different distribution of over-expressed SDPR mutants. Different GFP-tagged mutants of SDPR as indicated were over-expressed at similar levels in live HeLa cells and imaged by confocal microscopy. Bar 20μm. D. Mapping of the region of SDPR required for membrane targeting and tubulation. The diagram indicates a selected subset of all constructs analyzed, with a score representing their sub-cellular distribution based on up to 3 stars. Only over-expressing cells were analyzed - some mutants that are not membrane targeted when over-expressed are still found in caveolae when expressed at low levels, presumably because of binding to endogenous SDPR or another caveolar component. Construct 105-425 was occasionally observed in the nucleus as well as the cytosol.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2712677&req=5

Figure 5: SDPR over-expression induces membrane tubes derived from caveolaeA. Labeling of HeLa cells, two of which are over-expressing SDPR-GFP, with fluorescent antibodies against the GPI-linked protein CD59. Live cells were labeled for 20min prior to imaging. The lower panels show a magnified view of the region denoted by the dashed line. Confocal images. Bar 20μm. B. Localization of caveolin 1 to the ends of SDPR-mCh positive membrane tubes. Caveolin 1 was detected with polyclonal antibodies using indirect immunofluorescence. Bar 10μm. The lower panels show further examples of SDPR-induced membrane tubes with caveolin 1 puncta at one end. All images are confocal. C. Different distribution of over-expressed SDPR mutants. Different GFP-tagged mutants of SDPR as indicated were over-expressed at similar levels in live HeLa cells and imaged by confocal microscopy. Bar 20μm. D. Mapping of the region of SDPR required for membrane targeting and tubulation. The diagram indicates a selected subset of all constructs analyzed, with a score representing their sub-cellular distribution based on up to 3 stars. Only over-expressing cells were analyzed - some mutants that are not membrane targeted when over-expressed are still found in caveolae when expressed at low levels, presumably because of binding to endogenous SDPR or another caveolar component. Construct 105-425 was occasionally observed in the nucleus as well as the cytosol.
Mentions: Over-expression of SDPR causes accumulation of pronounced tubes in both HeLa and cav1−/− MEF cells, suggesting that SDPR may be able to stablize or generate membrane curvature. Labeling of HeLa cells with fluorescent antibodies against the plasma membrane marker CD59 confirmed that the SDPR-positive tubes are composed of plasma membrane derived membrane, and that these tubes are induced by expression of SDPR as they were not observed in non-transfected cells (Figure 5A). Expression of un-tagged SDPR also resulted in extensive membrane tubulation (Supplementary Figure 5B).

Bottom Line: Here we show that loss of SDPR (serum deprivation protein response) causes loss of caveolae.SDPR binds directly to PTRF and recruits PTRF to caveolar membranes.STB colocalizes extensively with both SDPR and caveolin 1.

View Article: PubMed Central - PubMed

Affiliation: MRC-LMB, Cambridge, UK.

ABSTRACT
Caveolae are plasma membrane invaginations with a characteristic flask-shaped morphology. They function in diverse cellular processes, including endocytosis. The mechanism by which caveolae are generated is not fully understood, but both caveolin proteins and PTRF (polymerase I and transcript release factor, also known as cavin) are important. Here we show that loss of SDPR (serum deprivation protein response) causes loss of caveolae. SDPR binds directly to PTRF and recruits PTRF to caveolar membranes. Overexpression of SDPR, unlike PTRF, induces deformation of caveolae and extensive tubulation of the plasma membrane. The B-subunit of Shiga toxin (STB) also induces membrane tubulation and these membrane tubes also originate from caveolae. STB colocalizes extensively with both SDPR and caveolin 1. Loss of caveolae reduces the propensity of STB to induce membrane tubulation. We conclude that SDPR is a membrane-curvature-inducing component of caveolae, and that STB-induced membrane tubulation is facilitated by caveolae.

Show MeSH
Related in: MedlinePlus