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Development (Cambridge, England) Apr 2016The spectrin cytoskeleton crosslinks actin to the membrane, and although it has been greatly studied in erythrocytes, much is unknown about its function in epithelia. We...
The spectrin cytoskeleton crosslinks actin to the membrane, and although it has been greatly studied in erythrocytes, much is unknown about its function in epithelia. We have studied the role of spectrins during epithelia morphogenesis using the Drosophila follicular epithelium (FE). As previously described, we show that α-Spectrin and β-Spectrin are essential to maintain a monolayered FE, but, contrary to previous work, spectrins are not required to control proliferation. Furthermore, spectrin mutant cells show differentiation and polarity defects only in the ectopic layers of stratified epithelia, similar to integrin mutants. Our results identify α-Spectrin and integrins as novel regulators of apical constriction-independent cell elongation, as α-Spectrin and integrin mutant cells fail to columnarize. Finally, we show that increasing and reducing the activity of the Rho1-Myosin II pathway enhances and decreases multilayering of α-Spectrin cells, respectively. Similarly, higher Myosin II activity enhances the integrin multilayering phenotype. This work identifies a primary role for α-Spectrin in controlling cell shape, perhaps by modulating actomyosin. In summary, we suggest that a functional spectrin-integrin complex is essential to balance adequate forces, in order to maintain a monolayered epithelium.
Topics: Actomyosin; Animals; Cell Differentiation; Cell Polarity; Cell Shape; Cytoskeleton; Drosophila; Drosophila Proteins; Epithelium; Female; Integrins; Mitosis; Mutation; Oocytes; Ovarian Follicle; Spectrin
PubMed: 26952981
DOI: 10.1242/dev.130070 -
Biochemical Society Transactions Nov 1992
Review
Topics: Alleles; Animals; Elliptocytosis, Hereditary; Gene Expression; Humans; Mutation; Spectrin
PubMed: 1487063
DOI: 10.1042/bst0200782 -
Nature Reviews. Neuroscience Apr 2023Spectrins are cytoskeletal proteins that are expressed ubiquitously in the mammalian nervous system. Pathogenic variants in SPTAN1, SPTBN1, SPTBN2 and SPTBN4, four of... (Review)
Review
Spectrins are cytoskeletal proteins that are expressed ubiquitously in the mammalian nervous system. Pathogenic variants in SPTAN1, SPTBN1, SPTBN2 and SPTBN4, four of the six genes encoding neuronal spectrins, cause neurological disorders. Despite their structural similarity and shared role as molecular organizers at the cell membrane, spectrins vary in expression, subcellular localization and specialization in neurons, and this variation partly underlies non-overlapping disease presentations across spectrinopathies. Here, we summarize recent progress in discerning the local and long-range organization and diverse functions of neuronal spectrins. We provide an overview of functional studies using mouse models, which, together with growing human genetic and clinical data, are helping to illuminate the aetiology of neurological spectrinopathies. These approaches are all critical on the path to plausible therapeutic solutions.
Topics: Animals; Mice; Humans; Spectrin; Nervous System Diseases; Neurons; Cell Membrane; Mammals
PubMed: 36697767
DOI: 10.1038/s41583-022-00674-6 -
Blood Feb 1987We recently showed that platelets contain submembranous actin filaments that are linked to glycoprotein (GP) Ib on the plasma membrane. In the present study, experiments...
We recently showed that platelets contain submembranous actin filaments that are linked to glycoprotein (GP) Ib on the plasma membrane. In the present study, experiments were performed to determine whether spectrin was associated with these filaments. The membrane-bound filaments were isolated from Triton X-100 (Sigma, St Louis) lysates of unstimulated platelets by differential centrifugation. Platelet spectrin was detected immunologically by using antibodies against human brain and RBC spectrin. Immunoblots showed that platelet spectrin consisted of two polypeptides (mol wt 240,000 and 235,000) that were similar in apparent mol wt to those of the alpha and beta chains of brain spectrin but differed slightly from those of RBC spectrin (mol wt 240,000 and 220,000). Immunoprecipitation experiments identified platelet spectrin as two minor polypeptides migrating on sodium dodecyl sulfate (SDS)-polyacrylamide gels between actin-binding protein (mol wt 250,000) and the platelet polypeptide P235 (mol wt 235,000). Immunoblots of fractions isolated from Triton X-100-lysed platelets revealed that the alpha and beta chains of platelet spectrin were associated almost entirely with the actin filaments that were linked to the plasma membrane. Little spectrin was recovered in the Triton X-100-soluble fraction or with the actin filaments that were not membrane bound. During activation of platelets with thrombin or ionophore A23187, the alpha and beta chains of spectrin were hydrolyzed, generating a major degradation product of mol wt 160,000 and a minor one of mol wt 170,000. These two hydrolytic products were also generated in Triton X-100 lysates incubated in the presence of Ca2+ but were not produced when lysates were treated with leupeptin, ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), or N-ethylmaleimide, known inhibitors of the Ca2+-dependent protease. These experiments show that spectrin is a previously unidentified component of the membrane-bound actin filament network and that hydrolysis of spectrin by the Ca2+-dependent protease may regulate the interactions of the filaments during platelet activation.
Topics: Adult; Blood Platelets; Calpain; Cytoskeleton; Humans; Hydrolysis; In Vitro Techniques; Spectrin
PubMed: 3026523
DOI: No ID Found -
Immunity Sep 2002With T cell receptor stimulation, intracellular pools of CD45 and spectrin move to the surface. These processes are coupled. In both peripheral lymphocytes and Jurkat T...
With T cell receptor stimulation, intracellular pools of CD45 and spectrin move to the surface. These processes are coupled. In both peripheral lymphocytes and Jurkat T cells, betaI spectrin and ankyrin associate with CD45. In Jurkat T cells, betaI spectrin peptides suppress surface recruitment of CD45 and CD3 and abrogate T cell activation. Other glycoproteins such as CD43 are not altered by the spectrin peptides. Spectrin's effects are mediated by ankyrin, which binds directly to the cytoplasmic domain of CD45 (K(d) = 4.3 +/- 3.0 nM). These data reveal a novel and unexpected contribution of the spectrin-ankyrin skeleton to the control of T lymphocyte function.
Topics: Ankyrins; CD3 Complex; Cell Membrane; Humans; Interleukin-2; Jurkat Cells; Leukocyte Common Antigens; Lymphocyte Activation; Macromolecular Substances; Membrane Glycoproteins; Neoplasm Proteins; Peptide Fragments; Protein Binding; Protein Interaction Mapping; Protein Isoforms; Protein Structure, Tertiary; Recombinant Fusion Proteins; Spectrin; Structure-Activity Relationship; T-Lymphocytes; Transfection
PubMed: 12354383
DOI: 10.1016/s1074-7613(02)00396-5 -
Journal of Cellular Biochemistry 1986Spectrin, the major component of the erythroid membrane skeleton, is a long, asymmetrical rodlike protein that interacts with several other proteins to form a... (Review)
Review
Spectrin, the major component of the erythroid membrane skeleton, is a long, asymmetrical rodlike protein that interacts with several other proteins to form a two-dimensional membrane skeleton. Progress in several laboratories over the past few years including substantial partial peptide and nucleotide sequence determination has greatly enhanced our knowledge of the structural properties of this large molecule (heterodimer = 465,000 daltons). The alpha and beta subunits are homologous with approximately 30% identity. They are aligned in an antiparallel side-to-side orientation with the amino- and carboxy-termini near opposite physical ends of the molecule. The predominant structural feature elucidated from sequencing this large molecule is the nearly universal occurrence in both subunits of a single type of repetitive structure. The periodicity of this homologous structure is exactly 106 amino acid residues. As many as 36 homologous, but nonidentical, repeats exist and comprise more than 90% of the mass of the heterodimer. Each of these repetitive units is folded into a triple-stranded structure that is highly helical. Peptide maps, antibody crossreactivity, peptide sequence analysis, and more recently nucleic acid sequences have defined several major properties of the erythroid molecule and related proteins in other tissues. Tissue-specific spectrins have the same 106-residue repetitive structure and show sequence homology to erythroid spectrin.
Topics: Amino Acid Sequence; Biological Evolution; Erythrocyte Membrane; Humans; Molecular Weight; Protein Conformation; Repetitive Sequences, Nucleic Acid; Sequence Homology, Nucleic Acid; Spectrin
PubMed: 3517024
DOI: 10.1002/jcb.240300306 -
Developmental Biology Mar 1988The role of spectrin and its association with calmodulin in spreading mouse blastomeres was investigated. Embryonic spectrin binds 125I-calmodulin in a calcium-dependent...
The role of spectrin and its association with calmodulin in spreading mouse blastomeres was investigated. Embryonic spectrin binds 125I-calmodulin in a calcium-dependent fashion in the blot overlay technique. Double-labeling experiments show coordinate redistribution of spectrin and calmodulin in blastomeres preparing to undergo active spreading movement. At this stage cortical spectrin staining is lost from the region of cell-substrate contact and spectrin and calmodulin become concentrated in two structures closely associated with the contacted region: a group of spherical bodies located on the cytoplasmic side of the cortical layer and a subcortical ring that marks the perimeter of the contacted region. The localization pattern of spectrin and calmodulin is also coordinated with that of actin and myosin. The results suggest that spectrin plays a role in the spreading of blastomeres and that this function may involve linkage of spectrin, calmodulin, and the cortical contractile apparatus.
Topics: Actins; Animals; Blastomeres; Calcium; Calmodulin; Electrophoresis, Polyacrylamide Gel; Fluorescent Antibody Technique; Immunoassay; Mice; Mice, Inbred ICR; Myosins; Spectrin
PubMed: 3277881
DOI: 10.1016/0012-1606(88)90237-0 -
The Journal of Neuroscience : the... Nov 1991Spectrin is a major component of the mammalian neuronal cytoskeleton. In the CNS, three isoforms of brain spectrin are known to exist: a cellular and dendritic isoform,...
Spectrin is a major component of the mammalian neuronal cytoskeleton. In the CNS, three isoforms of brain spectrin are known to exist: a cellular and dendritic isoform, (240/235E), related to neurons and glia; a cellular and axonal isoform, (240/235), related to neurons; and an isoform specific for astrocytes, (240/235A). In the present study, brain spectrins (240/235E) and (240/235) were localized within the mouse retina and optic nerve. Immunoblot analyses of proteins isolated from mouse retinas utilizing polyclonal antibodies to either brain spectrin (240/235) or brain spectrin (240/235E) revealed that these spectrins are present in the retina and that the two isoforms are the same molecular weights as those found in the brain. Immunocytochemical studies revealed that spectrin (240/235E) was localized in cell bodies of the inner nuclear, outer nuclear, and ganglion cell layers, and processes arborizing within the inner and outer plexiform layers. Spectrin (240/235) was distributed diffusely within the retina, lightly staining neurons in both the inner nuclear and outer nuclear layers, and the ganglion cell layer. In contrast to the situation found in the brain, spectrin (240/235) was but one of the axonal forms in the retina. We found that spectrin (240/235E) was also present in the axon-rich fiber layer and in the optic nerve and was often associated with fibrous elements. Spectrin (240/235) was also detected in the nerve fiber layer and optic nerve, but this isoform was not localized to fibers.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Immunohistochemistry; Isomerism; Mice; Mice, Inbred C57BL; Optic Nerve; Retina; Spectrin; Tissue Distribution
PubMed: 1941095
DOI: 10.1523/JNEUROSCI.11-11-03531.1991 -
Frontiers in Bioscience : a Journal and... Sep 2005The membrane-associated cytoskeleton of the cardiac muscle cell is emerging as an important element in the maintenance of normal cell functioning. Recently it was shown...
The membrane-associated cytoskeleton of the cardiac muscle cell is emerging as an important element in the maintenance of normal cell functioning. Recently it was shown that when proteins (betaII-spectrin, muscle Lim-only protein, ankyrin-B, ankyrin-G) of this system are defective or deficient, cardiac malfunction ensues. It is well-established that the spectrin cytoskeleton is associated with the plasma membrane, but it was only lately demonstrated that its components also lie on internal cell membranes. This is particularly apparent in muscle cells of the heart which contain specialised intracellular membrane compartments particular to this cell type such as the sarcoplasmic reticulum and T-tubules. Cardiomyocytes are subjected to constant mechanical stress. Since their mechanics are controlled through coordination of calcium fluxes mediated via cell membrane-based assemblies, it is imperative that these essential elements withstand the displacement forces of contraction. Cardiomyocyte spectrin locates the multifunctional spectrin/actin-binding and membrane-binding component, protein 4.1, and they act together on the plasma membrane as well as on internal membranes. We have found that cardiac protein 4.1 links to the calcium handling apparatus whilst spectrins connect with the sarcomeric contractile elements of the cell. Overall this assembly fulfils roles in stabilising cardiomyocyte cell membranes and in coordinating the macromolecular protein accumulations which regulate and accomplish cardiac molecular crosstalk, whilst at the same time enabling the muscle cells to resist extreme forces of contraction.
Topics: Animals; Calcium; Cytoskeletal Proteins; Cytoskeleton; Heart; Mammals; Mutation; Myocardium; Protein Isoforms; Spectrin
PubMed: 15970557
DOI: 10.2741/1759 -
PloS One 2016The kidney displays specialized regions devoted to filtration, selective reabsorption, and electrolyte and metabolite trafficking. The polarized membrane pumps,...
The kidney displays specialized regions devoted to filtration, selective reabsorption, and electrolyte and metabolite trafficking. The polarized membrane pumps, channels, and transporters responsible for these functions have been exhaustively studied. Less examined are the contributions of spectrin and its adapter ankyrin to this exquisite functional topography, despite their established contributions in other tissues to cellular organization. We have examined in the rodent kidney the expression and distribution of all spectrins and ankyrins by qPCR, Western blotting, immunofluorescent and immuno electron microscopy. Four of the seven spectrins (αΙΙ, βΙ, βΙΙ, and βΙΙΙ) are expressed in the kidney, as are two of the three ankyrins (G and B). The levels and distribution of these proteins vary widely over the nephron. αΙΙ/βΙΙ is the most abundant spectrin, found in glomerular endothelial cells; on the basolateral membrane and cytoplasmic vesicles in proximal tubule cells and in the thick ascending loop of Henle; and less so in the distal nephron. βΙΙΙ spectrin largely replaces βΙΙ spectrin in podocytes, Bowman's capsule, and throughout the distal tubule and collecting ducts. βΙ spectrin is only marginally expressed; its low abundance hinders a reliable determination of its distribution. Ankyrin G is the most abundant ankyrin, found in capillary endothelial cells and all tubular segments. Ankyrin B populates Bowman's capsule, podocytes, the ascending thick loop of Henle, and the distal convoluted tubule. Comparison to the distribution of renal protein 4.1 isoforms and various membrane proteins indicates a complex relationship between the spectrin scaffold, its adapters, and various membrane proteins. While some proteins (e.g. ankyrin B, βΙΙΙ spectrin, and aquaporin 2) tend to share a similar distribution, there is no simple mapping of different spectrins or ankyrins to most membrane proteins. The implications of this data are discussed.
Topics: Animals; Ankyrins; Blotting, Western; Cytoskeleton; Exons; Kidney; Membrane Proteins; Mice; Mice, Inbred C57BL; Microscopy, Fluorescence; Microscopy, Immunoelectron; Polymerase Chain Reaction; Protein Isoforms; RNA, Messenger; Specific Pathogen-Free Organisms; Spectrin
PubMed: 26727517
DOI: 10.1371/journal.pone.0142687