Filamentous substructure of microtubules of the marginal bundle of mammalian blood platelets

Behnke, O.; Zelander, T.

doi:10.1016/s0022-5320(67)80065-0

Cited by 89 publications

(28 citation statements)

References 27 publications

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“…It may be implied that they correspond to the openings of the endoplasmic reticulum found in the observation on sections (BEHNKE and ZELANDER, 1967;WHITE and KRIVIT 1967 a;BEHNKE, 1968).…”

Section: Discussionmentioning

confidence: 54%

Scanning Electron Microscopic Observations on Human Blood Platelets and Their Alterations Induced by Thrombin

Hattori

Tokunaga

Fujita

et al. 1969

Arch. Histol. Jap., Arch. Histol. Jpn

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“…It may be implied that they correspond to the openings of the endoplasmic reticulum found in the observation on sections (BEHNKE and ZELANDER, 1967;WHITE and KRIVIT 1967 a;BEHNKE, 1968).…”

Section: Discussionmentioning

confidence: 54%

Scanning Electron Microscopic Observations on Human Blood Platelets and Their Alterations Induced by Thrombin

Hattori

Tokunaga

Fujita

et al. 1969

Arch. Histol. Jap., Arch. Histol. Jpn

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“…Lateral association of the filaments may account for some of this heterogeneity but structures comparable in size and character to the 18 nm to 30 nm microtubules present as a circumferential bundle in whole cell preparations [35] do not appear to be formed in our procedure. Since a filamentous substructure with a centre to centre spacing of about 6 nm has been identified in microtubules present in platelet cytoplasm [35] the linear tubulin polymer produced in the present experiments may represent an intermediate stage in the microtubule assembly process.…”

Section: Discussionmentioning

confidence: 90%

Isolation of tubulin from pig platelets

Castle¹,

Crawford²

1975

FEBS Letters

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“…10 To determine genotypes by expression of the transgenic fusion protein, fetuses were stained with X-Gal and were incubated for 30 minutes in fixation buffer (100mM phosphate buffer containing 5mM EGTA (ethyleneglycoltetraacetic acid), 0.2% glutaraldehyde, and 2mM MgCl 2 ) and washed in 100mM phosphate buffer (pH 7.3) and 2mM MgCl 2 . Staining was performed for 6 hours or overnight at 37°C in staining buffer (5mM K 4 …”

Section: Mouse Husbandry Mk Culture and 5-bromo-4-chloro-3-indolylbmentioning

confidence: 99%

“…In wild-type platelets, this MT loop is normally coiled 8 to 12 times. 3 Ultrastructural data previously suggested that the platelet marginal bundle contains a single coiled filament, [3][4][5][6] and isolation of MT coils by platelet extraction affirmed this idea. However, the study by Patel-Hett et al 7 on living platelets revealed up to 7 free plus-ends, suggesting that several shorter MT filaments associate dynamically with one longer filament, forming a bipolar array.…”

Section: Introductionmentioning

confidence: 98%

The microtubule modulator RanBP10 plays a critical role in regulation of platelet discoid shape and degranulation

Kunert

Meyer

Fleischhauer

et al. 2009

Blood

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Terminally mature megakaryocytes undergo dramatic cellular reorganization to produce hundreds of virtually identical platelets. A hallmark feature of this process is the generation of an elaborate system of branched protrusions called proplatelets. We recently identified RanBP10 as a tubulin-binding protein that is concentrated along polymerized microtubules in mature megakaryocytes. RanBP10 depletion in vitro caused the disturbance of polymerized filaments.Here we study the function of RanBP10 in vivo by generating deficient mice using a gene-trap approach. Mutant mice show normal platelet counts, and fetal liverderived megakaryocytes reveal only slightly reduced proplatelet formation. However, ultrastructural analysis unveiled a significantly increased geometric axis ratio for resting platelets, and many platelets exhibited disorders in microtubule filament numbers and localization. Mutant mice showed a markedly prolonged bleeding time. Granule release, a process that depends on internal contraction of the microtubule marginal coil, also was reduced. Flow cytometry analysis revealed reduced expression of CD62P and CD63 after PAR4-peptide stimulation. These data suggest that RanBP10 plays an essential role in hemostasis and in maintaining microtubule dynamics with respect to both platelet shape and function. (Blood. 2009;114:5532-5540) IntroductionPlatelets develop from megakaryocytes (MKs), large polyploid cells localized in the bone marrow. Mature MKs rearrange their entire cytoplasm into pseudopod protrusions (designated proplatelets), a process that is driven by and dependent on microtubules (MTs). 1,2 MT filaments emanate from the cell cortex into the proplatelet tips, where they coil into a loop and later build the platelet marginal band. In wild-type platelets, this MT loop is normally coiled 8 to 12 times. 3 Ultrastructural data previously suggested that the platelet marginal bundle contains a single coiled filament, [3][4][5][6] and isolation of MT coils by platelet extraction affirmed this idea. However, the study by Patel-Hett et al 7 on living platelets revealed up to 7 free plus-ends, suggesting that several shorter MT filaments associate dynamically with one longer filament, forming a bipolar array.Each MT filament is composed of 13 protofilament heteropolymers of ␣-and ␤-tubulins. Mammalian genomes encode 6 ␣-tubulin and 5 ␤-tubulin genes. ␤1-tubulin (also referred to as class VI) is the most diverse isotype 8 and is found exclusively in cells that harbor a marginal band: MKs, platelets, and erythroblasts. 9 More than 90% of proplatelet MT filaments are composed of this ␤-tubulin isotype, 10 whose expression depends on the MK-specific transcription factor NF-E2. Genetically engineered mice that lack a functional Tubb1 gene are thrombocytopenic, and Tubb1 Ϫ/Ϫ platelets lack lentiform shape; the marginal band consists of only 2 to 3 coils, resulting in platelet spherocytosis. 11,12 Although ubiquitously expressed tubulin isotypes ␤2 and ␤5 are up-regulated, the equilibrium is shifted toward monomer...

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Filamentous substructure of microtubules of the marginal bundle of mammalian blood platelets

Cited by 89 publications

References 27 publications

Scanning Electron Microscopic Observations on Human Blood Platelets and Their Alterations Induced by Thrombin

Scanning Electron Microscopic Observations on Human Blood Platelets and Their Alterations Induced by Thrombin

Isolation of tubulin from pig platelets

The microtubule modulator RanBP10 plays a critical role in regulation of platelet discoid shape and degranulation

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