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PubMed1981

Human spectrin. VI. A viscometric study.

Employing viscometry, human spectrin heterodimers and heterotetramers were analyzed in aqueous solution containing different amounts of salt. (1) In aqueous 0.1 M NaCl, pH 7.5, at 4 degrees C, the intrinsic viscosity of isolated human spectrin heterodimers and heterotetramers was found to be 40 +/- 6 and 79 +/- 7 ml/g, respectively. (2) The intrinsic viscosity of isolated human spectrin heterodimers and heterotetramers increased to 78 +/- 8 and 180 +/- 10 ml/g, respectively, as the ionic strength of the solution was reduced to about 2 mM. (3) This viscometric study indicates that isolated human spectrin heterodimers and heterotetramers are flexible molecules with a contour length of at least 110 and 200 nm, respectively.

Electrophoresis, Polyacrylamide Gel↗
PubMed1990

Effect of the level of ATP and of the state of spectrin on osmotic properties of bovine erythrocytes.

The effect of the intracellular level of ATP and of the state of spectrin on the critical cell volume of bovine erythrocyte was studied. The state of spectrin was changed by thermal denaturation, which for the bovine red cell took place at similar temperature as for the human erythrocyte. The increase of the ATP level and the spectrin denaturation increased the critical cell volume, while metabolic starvation decreased it. The changes of the ATP level did not influence the critical volume after the denaturation of spectrin. The results suggest that the ATP-dependent effect on the critical cell volume was caused by an alteration of the membrane extensibility due to the change of the membrane skeleton-lipid bilayer interaction(s).

Adenosine Triphosphate↗
PubMed1994

Ankyrin inhibits binding of erythrocyte spectrin to phospholipid vesicles.

The studies on binding of erythrocyte spectrin to frozen and thawed phospholipid liposomes and its inhibition by ankyrin were performed. It was found that ankyrin inhibited up to 60% binding of spectrin by phosphatidylethanolamine/phosphatidylcholine vesicles. It was able to dissociate up to 40% of spectrin from this complex. Ankyrin inhibition of binding of phosphatidylserine/phosphatidylcholine vesicles by spectrin, although much lower, was also observed.

Animals↗
PubMed1978

Human spectrin. II. An electro-optic study.

The electrically induced birefringence of human spectrin heterodimer solutions has been studied. 1. Human spectrin heterodimers were found to have a specific Kerr constant Bsp = +(5 +/- 2) . 10(-11) m4/(V2 . kg). 2. Human spectrin exhibited a birefringence relaxation time tau decay = (2.0 +/- 0.3) microseconds. 3. The electro-optic study indicates that human spectrin heterodimers have a contour length of more than 40--50 nm.

Birefringence↗
PubMed1978

The breakdown of spectrin produced by ultrasonication.

The application of carefully controlled ultrasonication to human erythrocyte membranes (ghosts) has been found to produce a selective breakdown of the two spectrin polypeptides. This breakdown increases with the time and the intensity of ultrasonication. The 240 000 molecular weight spectrin polypeptide is slightly more susceptible to ultrasonication than the 220 000 molecular weight polypeptide. Isolated spectrin behaves in an identical manner when ultrasonicated. When highly purified samples of spectrin are ultrasonicated the progressive reduction of the molecular weight of the products with increasing time is clearly apparent.

Erythrocyte Membrane↗
PubMed1979

Specific fragmentation of human erythrocyte spectrin by chemical cleavage at cysteine residues.

Spectrin, isolated from human erythrocyte membrane, was specifically cleaved at the amino side of its cysteine residues by reacting it with 2-nitro-5-thiocyanobenzoic acid at pH 8.0 and incubating the product at pH 9.0. Conditions were developed to obtain quantitative cleavage, with virtually no side reactions due to exposure to the alkaline pH. The solubility and aggregation state of the spectrin fragments in 0.2 M sodium chloride, in 7 M guanidine hydrochloride or in 10 M urea, at pH 8.0, allow separation and partial purification of the fragments by gel filtration or by ion-exchange chromatography. Our results strongly suggest that various parts of the spectrin molecules have similar amino acid compositions. Due to the relatively limited number of fragments, this cleavage method is a promising tool for further elucidation of the structure of spectrin and for understanding its role in the erythrocyte membrane.

Amino Acids↗
PubMed1984

Reaction of phenylhydrazine with erythrocytes. Cross-linking of spectrin by disulfide exchange with oxidized hemoglobin.

Phenylhydrazine causes deleterious oxidations of components of erythrocytes. These reactions and their effects on the mechanical properties of rabbit erythrocytes are investigated to provide insight into the mechanisms leading to destruction of oxidatively damaged erythrocytes. After 1 hr of incubation with phenylhydrazine, precipitated denatured protein (Heinz body protein) amounts to 25-30% of membrane protein, but deformability of erythrocytes as measured by filtrability is unchanged. After 4 hr of incubation filtrability drops sharply. Polymerization of spectrin and covalent binding of hemoglobin to spectrin, but no peroxidation of membrane lipids is observed. Precipitated protein amounts to 85-95% of membrane protein. It contains Fe, porphyrin and globin peptide in the proportion 1:1:1. Heinz body protein precipitated when hemoglobin is incubated under similar conditions has 90% of its sulfhydryl groups oxidized and no other amino acids than cysteine are destroyed. Addition of this Heinz body protein to erythrocyte ghosts causes polymerization of spectrin. Incubation of tetrathionate, a specific cross-linking agent, causes filtrability to drop sharply after about 80 min. This effect is similar to that observed after 4 hr incubation with phenylhydrazine, and is accompanied by polymerization of spectrin and band 3. The results indicate that cross-linking of membrane proteins by disulfide exchange with precipitated hemoglobin may play a major role in decreasing deformability during incubation with phenylhydrazine.

Amino Acids↗
PubMed1995

Translational suppression of calpain I reduces NMDA-induced spectrin proteolysis and pathophysiology in cultured hippocampal slices.

Transfection of cultured hippocampal slices for five days with antisense oligonucleotides directed against mRNA encoding calpain I resulted in an approximately 60% decrease in the amount of caseinolytic activity stimulated by 10 microM calcium. Increases in a single proteolytic fragment of spectrin produced by 10-20 min of NMDA receptor stimulation were substantially (approximately 50%) reduced in antisense treated slices; this effect was not obtained in slices exposed to NMDA for 45 min. Attenuation of NMDA receptor-induced spectrin proteolysis by the antisense oligonucleotides was confirmed in immunoassays using antibodies that recognize multiple spectrin breakdown products and in immunocytochemical experiments with an antibody that detects an individual calpain I-mediated fragment. Translational suppression of calpain I did not detectably affect evoked synaptic responses but markedly improved their recovery from a 15 min infusion of NMDA. These results indicate that spectrin breakdown products provide a useful index of in situ calpain I activity and support the hypothesis that the protease plays a significant role in excitotoxicity.

Animals↗
PubMed1984

Co-expression of spectrin and fodrin in Friend erythroleukemic cells treated with DMSO.

Friend erythroleukemic cells can be used as a model of erythroid cell differentiation with the synthesis of the erythrocyte-specific products hemoglobin and spectrin stimulated by agents such as DMSO. In the present study we investigated the expression of both erythroid spectrin and non-erythroid fodrin in uninduced and DMSO-treated Friend cells. We report that both spectrin and fodrin co-exist at low levels in uninduced Friend cells and both are induced by treatment with DMSO. After longer times both spectrin and fodrin appear to undergo rearrangements into submembranous 'patches' and 'caps'. Although both molecules co-localize in most of these cells, they can be independently immunoprecipitated, suggesting that significant amounts of hybrid molecules are not formed.

Animals↗
PubMed1985

Effect of spectrin dimer on actin polymerization.

Spectrin dimer is shown to influence the polymerization behaviour of actin. The polymerization of both Mg2+- and Ca2+-actin is regulated by an enhancement in the rate of nucleation and a fragmentation of preformed actin filaments. In addition, spectrin decreases the critical concentration of Ca2+-actin but not that of Mg2+-actin. This suggests that the two types of actin may differ in their interaction with spectrin dimer probably due to the different conformations. Band 4.1 elevates the effects of spectrin under non-equilibrium conditions but its contribution is less at steady state.

Actins↗
PubMed1987

Alpha-actinin and spectrin have common structural domains.

The alpha- and beta-subunits of spectrin are made of repeated homologous units of 106 residues. In the recently reported partial sequence of the chicken non-muscle alpha-actinin, a repetitive sequence homologous to the internal repeat in spectrin occurs several times. Both spectrin and alpha-actinin are components of the cytoskeletal network, the integrity of which is based on multiple and complex interactions. We suggest that the shared domain structure indicates common structural principles or interactions of spectrin and alpha-actinin and reflects their common evolution.

Actinin↗
PubMed1990

Association of brain spectrin isoforms with microtubules.

The relationship of rat brain spectrin isoforms to microtubules of newborn and adult animals was studied. Spectrins were minor components in microtubule preparations. The microtubule-associated spectrin is a major calmodulin-binding protein. Radiolabelled brain spectrin(240/235) revealed specific microtubule binding activity in vitro, possibly via a tubulin.

Age Factors↗
PubMed1991

Identification of a 220 kDa membrane-associated plant cell protein immunologically related to human beta-spectrin.

Electrophoretic analysis of low ionic strength extracts of tomato plant leaves revealed the presence of two proteins of apparent molecular weights of 240 kDa and 220 kDa which co-migrated with purified human erythrocyte alpha- and beta-spectrin subunits. Immunochemical analyses employing an affinity-purified polyclonal antibody to human erythrocyte beta-spectrin reacted specifically with the 220 kDa plant cell protein. Immunofluorescence microscopy indicated that the beta-spectrin antibody recognized an antigen which was primarily restricted to the peripheral areas of the cells. Collectively, these results suggest that the cells of higher plants contain polypeptides related to the spectrin family of proteins. It is proposed that the plant cell possesses a membrane skeleton which is structurally and perhaps functionally analogous to that of the animal cell.

Chromatography, Affinity↗
PubMed1990

In vitro digestion of spectrin, protein 4.1 and ankyrin by erythrocyte calcium dependent neutral protease (calpain I).

1. In whole ghosts, ankyrin, protein 4.1, protein band 3 and spectrin are lysed by purified calpain I in the presence of calcium. 2. Limited calpain lysis of purified ankyrin results in several peptides, including a 85 kD peptide bearing the ankyrin interaction site for the protein band 3 internal fragment (43 kD), and a 55 kD peptide carrying the ankyrin-spectrin interaction site. 3. These peptides are differently phosphorylated: the 85 kD by cytosol casein kinase, and the 55 kD by membrane casein kinase. 4. Protein 4.1 lysis mainly produces a 30 kD peptide resistant to proteolysis. 5. The spectrin beta-chain is more sensitive to calpain cleavage than the alpha chain; both chains seem to be cleaved in a similar sequential manner. 6. Limited proteolysis of spectrin dimer does not impede tetramerization in vitro.

Ankyrins↗
PubMed1976

Erythrocyte spectrin peak II phosphorylation in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a rapidly progressive crippling disease of young boys that is inherited as an X-linked recessive trait. Previous studies have demonstrated the usefulness of erythrocyte studies in exploring membrane abnormalities in inheritied muscular dystrophy. Erythrocyte spectrin peak II protein (m.w. equivalent to 220,000) was more highly phosphorylated under initial rate conditions in DMD than in controls. The extent of peak II phosphorylation was greater in DMD erythrocytes and a Na+ stimulated peak II phosphorylation effect (Avruch and Fairbanks 1974) was not found to account for the differences between DMD and controls. The phosphorylated state of spectrin proteins in the membrane was evaluated and no differences in DMD could be measured. The maximal transfer of phosphate from differences in DMD could be measured. The maximal transfer of phosphate from [gamma-32P]ATP to spectrin peak II accounts for approximately 5-10% of the total phosphate content of spectrin.

Adenosine Triphosphate↗
PubMed1993

Nucleotide sequence of a cDNA for canine beta-spectrin reveals high evolutionary conservation.

A cDNA coding for the carboxy-terminus of canine beta-spectrin was isolated from a canine tracheal cDNA library. Analysis of the 3267 nucleotide sequence revealed a single open reading frame coding for 707 amino acids. Comparison of the deduced amino acid sequence to that of the recently reported general isoform of human beta-spectrin (beta G) revealed 98% identity. This high degree of conservation of the general isoform of beta-spectrin illustrates a strong evolutionary selection and should help in identification of sites that are candidates to mediate specialized functions of this general isoform. This is the first report of a cDNA encoding canine beta-spectrin.

Amino Acid Sequence↗
PubMed1990

Isolation of rat liver spectrin and identification of functional domains.

Immunohistochemical studies carried out with liver sections show that spectrin is uniformly distributed along the whole plasma membrane of hepatocytes. The bilecanalicular spectrin is released during the purification of liver subplasma membrane fractions, whereas most of the basolateral spectrin remains tightly bound to the membrane. Spectrin associated with the basolateral membranes has been purified and its subunits isolated. The alpha-subunit retains the ability to bind both calmodulin and actin. Fragments have been obtained either by chemical or by proteolytical digestion of the 240 kDa alpha-subunit. Treatment with CNBr yields fragments of about 30 kDa which bind actin and calmodulin. Digestion with Staphylococcus aureus V-8 proteinase yields a calmodulin-binding fragment of 27 kDa and an actin-binding fragment of 31 kDa.

Actins↗
PubMed1992

Secretagogue-induced proteolysis of lung spectrin in alveolar epithelial type II cells.

Incubation of isolated rat alveolar epithelial type II cells with secretagogues (calcium ionophore, ATP or terbutaline) resulted in rapid proteolysis of lung spectrin and appearance of multiple proteolytic products which showed immunoreactivity with an antibody against human erythrocyte spectrin. These proteolytic products were similar to those generated from erythrocyte spectrin or cultured lung tumor cells (A549 cells) incubated with purified calpain. Furthermore, incubation of alveolar type II cells with a calpain-specific inhibitor modulated the secretagogue-induced proteolysis of lung spectrin. Thus, stimulation of secretion appeared to activate endogenous calpain in type II cells, suggesting that calpain-mediated proteolysis of a submembranous cytoskeletal protein could play an important role in the secretory process.

Adenosine Triphosphate↗