Sequential Degradation of αII and βII Spectrin by Calpain in Glutamate or Maitotoxin-Stimulated Cells

Glantz, Susan B.; Cianci, Carol D.; Iyer, Rathna; Pradhan, Deepti; Wang, Kevin; Morrow, Jon S.

doi:10.1021/bi061504y

Cited by 38 publications

(53 citation statements)

References 81 publications

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“…A␤ treatment leads to the rapid fragmentation of spectrin, producing a 150-kDa product, consistent with calpain digestion, which is effectively blocked by the calpain inhibitor (Fig. 3C) (39). On the other hand, spectrin cleavage is not blocked by pretreatment with the caspase 3/7 inhibitor (data not shown).…”

Section: Significant Cell Death Of Primary Rat Hippocampal Cultures Osupporting

confidence: 51%

Amyloid β-Mediated Cell Death of Cultured Hippocampal Neurons Reveals Extensive Tau Fragmentation without Increased Full-length Tau Phosphorylation

Reifert¹,

Hartung-Cranston²,

Feinstein

2011

Journal of Biological Chemistry

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A variety of genetic and biochemical evidence suggests that amyloid ␤ (A␤) oligomers promote downstream errors in Tau action, in turn inducing neuronal dysfunction and cell death in Alzheimer and related dementias. To better understand molecular mechanisms involved in A␤-mediated neuronal cell death, we have treated primary rat hippocampal cultures with A␤ oligomers and examined the resulting cellular changes occurring before and during the induction of cell death with a focus on altered Tau biochemistry. The most rapid neuronal responses upon A␤ administration are activation of caspase 3/7 and calpain proteases. A␤ also appears to reduce Akt and Erk1/2 kinase activities while increasing GSK3␤ and Cdk5 activities. Shortly thereafter, substantial Tau degradation begins, generating relatively stable Tau fragments. Only a very small fraction of fulllength Tau remains intact after 4 h of A␤ treatment. In conflict with expectations based on suggested increases of GSK3␤ and Cdk5 activities, A␤ does not cause any major increases in phosphorylation of full-length Tau as assayed by immunoblotting one-dimensional gels with 11 independent site-and phosphospecific anti-Tau antibodies as well as by immunoblotting twodimensional gels probed with a pan-Tau antibody. There are, however, subtle and transient increases in Tau phosphorylation at 3-4 specific sites before its degradation. Taken together, these data are consistent with the notion that A␤-mediated neuronal cell death involves the loss of full-length Tau and/or the generation of toxic fragments but does not involve or require hyperphosphorylation of full-length Tau.Many neurodegenerative diseases are characterized by the accumulation of aggregated proteins in the brain. For example, the microtubule-associated protein Tau forms aggregates in a variety of neurodegenerative diseases known as tauopathies, including Alzheimer, frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), progressive supranuclear palsy, corticobasal degeneration, and related dementias (1, 2). Alzheimer disease is distinguished from many other tauopathies by accumulation of a second pathological feature known as amyloid ␤ (A␤) 3 plaques (3, 4). Complementary genetic evidence demonstrates that errors in the action or regulation of either Tau or the amyloid precursor protein (which is proteolytically cleaved to produce A␤) can cause neuronal cell death and dementia in humans (5). Furthermore, experiments in both cultured rodent hippocampal neurons and transgenic mice demonstrate that A␤-mediated neuronal cell death and memory deficits require Tau (6, 7). Taken together, the data suggest an intrinsic relationship between A␤ and Tau dysfunction. Indeed, the widely cited "amyloid cascade hypothesis" proposes that A␤ oligomers induce aberrant effects on Tau, which in turn promotes neurodegeneration and dementia (8 -10).One central feature of Alzheimer and related dementias is that Tau isolated from affected brains is hyperphosphorylated (11,12). This observation led investigators to ...

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Section: Significant Cell Death Of Primary Rat Hippocampal Cultures Osupporting

confidence: 51%

Amyloid β-Mediated Cell Death of Cultured Hippocampal Neurons Reveals Extensive Tau Fragmentation without Increased Full-length Tau Phosphorylation

Reifert¹,

Hartung-Cranston²,

Feinstein

2011

Journal of Biological Chemistry

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“…␣2 spectrin is also strongly expressed (Figure 2A,C), although much of the native subunit was processed by proteolytic cleavage, as reported previously in other cells. 29,30 Neither nonerythroid spectrin isoform antibody reacted against erythrocyte ghost proteins, indicating specificity for only the nonerythroid forms. Because both platelets and erythrocytes derive from a common myeloid progenitor cell, we also examined proplatelets and platelets for expression of the erythroid ␣1 and ␤1 spectrins.…”

Section: Structure Of the Proplatelet Membrane Skeleton And Identificmentioning

confidence: 95%

The spectrin-based membrane skeleton stabilizes mouse megakaryocyte membrane systems and is essential for proplatelet and platelet formation

Patel–Hett

Wang

Begonja

et al. 2011

Blood

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Megakaryocytes generate platelets by remodeling their cytoplasm first into proplatelets and then into preplatelets, which undergo fission to generate platelets. Although the functions of microtubules and actin during platelet biogenesis have been defined, the role of the spectrin cytoskeleton is unknown. We investigated the function of the spectrin-based membrane skeleton in proplatelet and platelet production in murine megakaryocytes. Electron microscopy revealed that, like circulating platelets, proplatelets have a dense membrane skeleton, the main fibrous component of which is spectrin. Unlike other cells, megakaryocytes and their progeny express both erythroid and nonerythroid spectrins. Assembly of spectrin into tetramers is required for invaginated membrane system maturation and proplatelet extension, because expression of a spectrin tetramer-disrupting construct in megakaryocytes inhibits both processes. Incorporation of this spectrindisrupting fragment into a novel permeabilized proplatelet system rapidly destabilizes proplatelets, causing blebbing and swelling. Spectrin tetramers also stabilize the "barbell shapes" of the penultimate stage in platelet production, because addition of the tetramer-disrupting construct converts these barbell shapes to spheres, demonstrating that membrane skeletal continuity maintains the elongated, pre-fission shape. The results of this study provide evidence for a role for spectrin in different steps of megakaryocyte development through its participation in the formation of invaginated membranes and in the maintenance of proplatelet structure. (Blood. 2011;118(6): 1641-1652) IntroductionBlood platelets, like erythrocytes, must withstand high shear forces during circulation. Retaining their discoid shape is critical to platelets, because their small size and shape cause them to be propelled by blood flow to the endothelial surface, where they are positioned to readily sense and respond to vascular damage. To provide structural support and prevent gross deformations as they circulate, mature platelets contain a robust membrane skeleton that is formed by spectrin molecules, adducin, and actin filament barbed ends. [1][2][3] Two thousand spectrin tetramers, 200-nm-long head-tohead assemblies of ␣␤ heterodimers, compose the bulk of this 2D network. Although less is known about how the spectrin-actin network forms and connects to the plasma membrane in platelets relative to erythrocytes, certain differences between the 2 membrane skeletons have been recognized. First, spectrin strands comprising the platelet membrane skeleton interconnect on the ends of long actin filaments originating from the cytoplasm instead of short actin oligomers. [3][4][5] Therefore, the platelet spectrin lattice and its associated actin filaments assemble into a continuous ultrastructure. Second, tropomodulins do not appear to have a major role in capping actin filament pointed ends, as occurs in erythrocytes. 6,7 Instead, a substantial number of these ends exist free or are capped by Arp2/3 in the res...

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“…To measure the level of calpain activation in pulmonary arterioles, SBDP was detected as described previously (65,66). Spectrin contains a specific calpain cleavage site and releases SBDP (67), which can be detected by antibody.…”

Section: Figure 14mentioning

confidence: 99%

“…Spectrin contains a specific calpain cleavage site and releases SBDP (67), which can be detected by antibody. This is a widely accepted method to detect calpain activation in vivo (65,66,68). Lung slides of 7-μm thickness were incubated first with a rabbit polyclonal antibody against SBDP (developed by our laboratory) and mouse monoclonal antibody against α-actin overnight and then with goat anti-rabbit IgG-Alexa Fluor 488 and goat anti-mouse IgG-Alexa…”

Section: Figure 14mentioning

confidence: 99%

Calpain mediates pulmonary vascular remodeling in rodent models of pulmonary hypertension, and its inhibition attenuates pathologic features of disease

Han

Greer³

et al. 2011

J. Clin. Invest.

105

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Pulmonary hypertension is a severe and progressive disease, a key feature of which is pulmonary vascular remodeling. Several growth factors, including EGF, PDGF, and TGF-β1, are involved in pulmonary vascular remodeling during pulmonary hypertension. However, increased knowledge of the downstream signaling cascades is needed if effective clinical interventions are to be developed. In this context, calpain provides an interesting candidate therapeutic target, since it is activated by EGF and PDGF and has been reported to activate TGF-β1. Thus, in this study, we examined the role of calpain in pulmonary vascular remodeling in two rodent models of pulmonary hypertension. These data showed that attenuated calpain activity in calpain-knockout mice or rats treated with a calpain inhibitor resulted in prevention of increased right ventricular systolic pressure, right ventricular hypertrophy, as well as collagen deposition and thickening of pulmonary arterioles in models of hypoxia-and monocrotaline-induced pulmonary hypertension. Additionally, inhibition of calpain in vitro blocked intracellular activation of TGF-β1, which led to attenuated Smad2/3 phosphorylation and collagen synthesis. Finally, smooth muscle cells of pulmonary arterioles from patients with pulmonary arterial hypertension showed higher levels of calpain activation and intracellular active TGF-β. Our data provide evidence that calpain mediates EGF-and PDGF-induced collagen synthesis and proliferation of pulmonary artery smooth muscle cells via an intracrine TGF-β1 pathway in pulmonary hypertension. IntroductionPulmonary hypertension is a severe and progressive disease characterized by increased pulmonary vascular resistance leading to right heart failure and death (1-3). Pulmonary vascular remodeling is an important common pathological feature of all categories of pulmonary hypertension. Accumulation of extracellular matrix, including collagen, and vascular smooth muscle cell proliferation and hypertrophy contribute to medial hypertrophy and muscularization, leading to obliteration of precapillary pulmonary arteries and sustained elevation of pulmonary arterial pressure (3, 4).Several growth factors, including EGF, PDGF, and TGF-β1, participate in the process of pulmonary vascular remodeling in patients with pulmonary hypertension and in animal models (2,(5)(6)(7)(8). For example, expression of EGF or its receptor EGFR are increased in animal models of monocrotaline-(MCT-) and hypoxia-induced pulmonary hypertension and in humans with pulmonary hypertension (8-10). Blockade of EGFR results in reductions in pulmonary pressure, right ventricular hypertrophy, and distal arterial muscularization in MCT-induced pulmonary hypertension (11). Moreover, PDGF and its receptor are upregulated in pulmonary arteries of patients with pulmonary hypertension (12, 13) and rodents exposed to chronic hypoxia and MCT (7,14,15). PDGF receptor antagonists not only prevent, but also reverse, increased

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Sequential Degradation of αII and βII Spectrin by Calpain in Glutamate or Maitotoxin-Stimulated Cells

Cited by 38 publications

References 81 publications

Amyloid β-Mediated Cell Death of Cultured Hippocampal Neurons Reveals Extensive Tau Fragmentation without Increased Full-length Tau Phosphorylation

Amyloid β-Mediated Cell Death of Cultured Hippocampal Neurons Reveals Extensive Tau Fragmentation without Increased Full-length Tau Phosphorylation

The spectrin-based membrane skeleton stabilizes mouse megakaryocyte membrane systems and is essential for proplatelet and platelet formation

Calpain mediates pulmonary vascular remodeling in rodent models of pulmonary hypertension, and its inhibition attenuates pathologic features of disease

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