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Proceedings of the National Academy of... Feb 2017The remarkable hearing capacities of mammals arise from various evolutionary innovations. These include the cochlear outer hair cells and their singular feature, somatic...
The remarkable hearing capacities of mammals arise from various evolutionary innovations. These include the cochlear outer hair cells and their singular feature, somatic electromotility, i.e., the ability of their cylindrical cell body to shorten and elongate upon cell depolarization and hyperpolarization, respectively. To shed light on the processes underlying the emergence of electromotility, we focused on the βV giant spectrin, a major component of the outer hair cells' cortical cytoskeleton. We identified strong signatures of adaptive evolution at multiple sites along the spectrin-βV amino acid sequence in the lineage leading to mammals, together with substantial differences in the subcellular location of this protein between the frog and the mouse inner ear hair cells. In frog hair cells, spectrin βV was invariably detected near the apical junctional complex and above the cuticular plate, a dense F-actin meshwork located underneath the apical plasma membrane. In the mouse, the protein had a broad punctate cytoplasmic distribution in the vestibular hair cells, whereas it was detected in the entire lateral wall of cochlear outer hair cells and had an intermediary distribution (both cytoplasmic and cortical, but restricted to the cell apical region) in cochlear inner hair cells. Our results support a scenario where the singular organization of the outer hair cells' cortical cytoskeleton may have emerged from molecular networks initially involved in membrane trafficking, which were present near the apical junctional complex in the hair cells of mammalian ancestors and would have subsequently expanded to the entire lateral wall in outer hair cells.
Topics: Actins; Adaptation, Biological; Animals; Birds; Cell Movement; Computer Simulation; Electrophysiological Phenomena; Hair Cells, Auditory, Inner; Hair Cells, Auditory, Outer; HeLa Cells; Hearing; Humans; Mammals; Mice; Mutation; Phylogeny; Spectrin; Xenopus laevis
PubMed: 28179572
DOI: 10.1073/pnas.1618778114 -
BioEssays : News and Reviews in... Jul 1986
Topics: Animals; Brain; Brain Chemistry; Mice; Molecular Weight; Spectrin
PubMed: 3790130
DOI: 10.1002/bies.950050108 -
Biochimica Et Biophysica Acta. Proteins... Nov 2019Spectrin, the major protein component of the erythrocyte membrane skeleton has chaperone like activity and is known to bind membrane phospholipids and hemoglobin. We...
Spectrin, the major protein component of the erythrocyte membrane skeleton has chaperone like activity and is known to bind membrane phospholipids and hemoglobin. We have probed the chaperone activity of spectrin in presence of hemoglobin and phospholipid SUVs of different compositions to elucidate the effect of phospholipid/hemoglobin binding on chaperone function. It is seen that spectrin displays a preference for hemoglobin over other substrates leading to a decrease in chaperone activity in presence of hemoglobin. A competition is seen to exist between phospholipid binding and chaperone function of spectrin, in a dose dependent manner with the greatest extent of decrease being seen in case of phospholipid vesicles containing aminophospholipids e.g. PS and PE which may have implications in diseases like hereditary spherocytosis where mutation in spectrin is implicated in its detachment from cell membrane. To gain a clearer understanding of the chaperone like activity of spectrin under in-vivo like conditions we have investigated the effect of macromolecular crowders as well as phosphorylation and glycation states on chaperone activity. It is seen that the presence of non-specific, protein and non-protein macromolecular crowders do not appreciably affect chaperone function. Phosphorylation also does not affect the chaperone function unlike glycation which progressively diminishes chaperone activity. We propose a model where chaperone clients adsorb onto spectrin's surface and processes that bind to and occlude these surfaces decrease chaperone activity.
Topics: Animals; Cattle; Erythrocyte Membrane; Hemoglobins; Molecular Chaperones; Phospholipids; Sheep; Spectrin
PubMed: 31470132
DOI: 10.1016/j.bbapap.2019.140267 -
The Journal of Cell Biology Nov 1987We purified a protein from Drosophila S3 tissue culture cells that has many of the diagnostic features of spectrin from vertebrate organisms: (a) The protein consists of...
We purified a protein from Drosophila S3 tissue culture cells that has many of the diagnostic features of spectrin from vertebrate organisms: (a) The protein consists of two equimolar subunits (Mr = 234 and 226 kD) that can be reversibly cross-linked into a complex composed of equal amounts of the two subunits. (b) Electron microscopy of the native molecule reveals two intertwined, elongated strands with a contour length of 180 nm. (c) Antibodies directed against vertebrate spectrin react with the Drosophila protein and, similarly, antibodies to the Drosophila protein react with vertebrate spectrins. One monoclonal antibody has been found to react with both of the Drosophila subunits and with both subunits of vertebrate brain spectrin. (d) The Drosophila protein exhibits both actin-binding and calcium-dependent calmodulin-binding activities. Based on the above criteria, this protein appears to be a bona fide member of the spectrin family of proteins.
Topics: Actins; Animals; Antibodies; Antibodies, Monoclonal; Antigen-Antibody Complex; Calmodulin; Cell Line; Drosophila; Macromolecular Substances; Microscopy, Electron; Molecular Weight; Spectrin
PubMed: 3680372
DOI: 10.1083/jcb.105.5.2095 -
Neuroscience Letters Aug 1991Brain spectrin is a major membrane skeleton protein that participates in cellular transport, cell morphogenesis, neurotransmitter release and growth cone adhesion. The...
Brain spectrin is a major membrane skeleton protein that participates in cellular transport, cell morphogenesis, neurotransmitter release and growth cone adhesion. The present study showed that in Alzheimer disease (AD) neuropil, brain spectrin immunoreactivity is co-localized with synaptophysin in the presynaptic boutons. At the ultrastructural level, brain spectrin immunoreactivity was observed in the presynaptic terminals and in the axoplasm of some myelinated and unmyelinated fibers. In addition to this normal localization of brain spectrin in the AD brain, we also found brain spectrin immunoreactivity associated with abnormal patchy lesions in the AD neuropil. Confocal laser imaging and immunoelectron microscopy revealed that these lesions corresponded to thick cellular processes derived from neurons. The findings that these structures were anti-neurofilament positive but anti-glial fibrillary acidic protein (GFAP) and Ricinus communis agglutinin I (RCA-I) negative confirm their neuronal origin, and rule out the possibility of glial origin. These structures could represent either atypical axonal or dendritic processes derived from sprouting neurons or the accumulation of brain spectrin degradation products in degenerating neurons.
Topics: Aged; Alzheimer Disease; Brain; Brain Chemistry; Glial Fibrillary Acidic Protein; Humans; Microscopy, Immunoelectron; Middle Aged; Neurons; Spectrin
PubMed: 1922957
DOI: 10.1016/0304-3940(91)90707-z -
The Journal of Cell Biology Jul 2014Ankyrin-G and βII-spectrin colocalize at sites of cell-cell contact in columnar epithelial cells and promote lateral membrane assembly. This study identifies two...
Ankyrin-G and βII-spectrin colocalize at sites of cell-cell contact in columnar epithelial cells and promote lateral membrane assembly. This study identifies two critical inputs from lipids that together provide a rationale for how ankyrin-G and βII-spectrin selectively localize to Madin-Darby canine kidney (MDCK) cell lateral membranes. We identify aspartate-histidine-histidine-cysteine 5/8 (DHHC5/8) as ankyrin-G palmitoyltransferases required for ankyrin-G lateral membrane localization and for assembly of lateral membranes. We also find that βII-spectrin functions as a coincidence detector that requires recognition of both ankyrin-G and phosphoinositide lipids for its lateral membrane localization. DHHC5/8 and βII-spectrin colocalize with ankyrin-G in micrometer-scale subdomains within the lateral membrane that are likely sites for palmitoylation of ankyrin-G. Loss of either DHHC5/8 or ankyrin-G-βII-spectrin interaction or βII-spectrin-phosphoinositide recognition through its pleckstrin homology domain all result in failure to build the lateral membrane. In summary, we identify a functional network connecting palmitoyltransferases DHHC5/8 with ankyrin-G, ankyrin-G with βII-spectrin, and βII-spectrin with phosphoinositides that is required for the columnar morphology of MDCK epithelial cells.
Topics: Animals; Ankyrins; Cell Membrane; Cell Polarity; Dogs; Epithelial Cells; Gene Knockdown Techniques; Lipoylation; Membrane Proteins; Models, Biological; Phosphatidylinositols; Spectrin
PubMed: 25049274
DOI: 10.1083/jcb.201401016 -
Biophysical Journal Apr 2008Spectrin (Sp), a key component of the erythrocyte membrane, is routinely stretched to near its fully folded contour length during cell deformations. Such dynamic loading...
Spectrin (Sp), a key component of the erythrocyte membrane, is routinely stretched to near its fully folded contour length during cell deformations. Such dynamic loading may induce domain unfolding as suggested by recent experiments. Herein we develop a model to describe the folding/unfolding of spectrin during equilibrium or nonequilibrium extensions. In both cases, our model indicates that there exists a critical extension beyond which unfolding occurs. We further deploy this model, together with a three-dimensional model of the junctional complex in the erythrocyte membrane, to explore the effect of Sp unfolding on the membrane's mechanical properties, and on the thermal fluctuation of membrane-attached beads. At large deformations our results show a distinctive strain-induced unstiffening behavior, manifested in the slow decrease of the shear modulus, and accompanied by an increase in bead fluctuation. Bead fluctuation is also found to be influenced by mode switching, a phenomenon predicted by our three-dimensional model. The amount of stiffness reduction, however, is modest compared with that reported in experiments. A possible explanation for the discrepancy is the occurrence of spectrin head-to-head disassociation which is also included within our modeling framework and used to analyze bead motion as observed via experiment.
Topics: Computer Simulation; Elasticity; Erythrocyte Membrane; Membrane Fluidity; Membrane Proteins; Models, Cardiovascular; Models, Chemical; Models, Molecular; Protein Conformation; Protein Denaturation; Protein Folding; Spectrin; Stress, Mechanical
PubMed: 18065469
DOI: 10.1529/biophysj.107.119438 -
Scientific Reports Mar 2021The neuronal membrane-associated periodic spectrin skeleton (MPS) contributes to neuronal development, remodeling, and organization. Post-translational modifications...
The neuronal membrane-associated periodic spectrin skeleton (MPS) contributes to neuronal development, remodeling, and organization. Post-translational modifications impinge on spectrin, the major component of the MPS, but their role remains poorly understood. One modification targeting spectrin is cleavage by calpains, a family of calcium-activated proteases. Spectrin cleavage is regulated by activated calpain, but also by the calcium-dependent binding of calmodulin (CaM) to spectrin. The physiologic significance of this balance between calpain activation and substrate-level regulation of spectrin cleavage is unknown. We report a strain of C57BL/6J mice harboring a single αII spectrin point mutation (Sptan1 c.3293G > A:p.R1098Q) with reduced CaM affinity and intrinsically enhanced sensitivity to calpain proteolysis. Homozygotes are embryonic lethal. Newborn heterozygotes of either gender appear normal, but soon develop a progressive ataxia characterized biochemically by accelerated calpain-mediated spectrin cleavage and morphologically by disruption of axonal and dendritic integrity and global neurodegeneration. Molecular modeling predicts unconstrained exposure of the mutant spectrin's calpain-cleavage site. These results reveal the critical importance of substrate-level regulation of spectrin cleavage for the maintenance of neuronal integrity. Given that excessive activation of calpain proteases is a common feature of neurodegenerative disease and traumatic encephalopathy, we propose that damage to the spectrin MPS may contribute to the neuropathology of many disorders.
Topics: Animals; Calpain; Cerebellar Ataxia; Cerebellum; Mice; Mice, Inbred C57BL; Point Mutation; Protein Binding; Proteolysis; Spectrin
PubMed: 33790315
DOI: 10.1038/s41598-021-86470-1 -
Protein Profile 1994
Review
Topics: Actinin; Amino Acid Sequence; Animals; Binding Sites; Dystrophin; Humans; Membrane Glycoproteins; Microfilament Proteins; Models, Molecular; Molecular Sequence Data; Sequence Alignment; Spectrin
PubMed: 8624824
DOI: No ID Found -
NatureHereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the...
Hereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the spectrin-actin membrane skeleton, leading to loss of surface membrane. Recessively inherited spectrin deficiency with extreme erythrocyte fragility and spherocytosis has been identified in certain mutant mice and two severely anaemic humans. Although suspected, deficiency of spectrin has not been demonstrated in less severe forms of human HS. We not report the quantitation of erythrocytes spectrin by radioimmunoassay. We found that normal erythrocytes contained 240,000 copies of spectrin heterodimer, whereas erythrocytes from 14 patients with a variety of types of HS were all partially deficient in spectrin (range 74,000-200,000 copies), the magnitude of the deficiency correlating with the severity of the disease. Spectrin deficiency of varying degrees is common in HS and probably represents the principal structural defect leading to loss of surface membrane.
Topics: Erythrocytes; Humans; Osmotic Fragility; Radioimmunoassay; Spectrin; Spherocytosis, Hereditary
PubMed: 3982506
DOI: 10.1038/314380a0