Two classes of collagen-tailed, asymmetric molecular forms of acetylcholinesterase in skeletal muscle: differential effects of denervation

Barat, Ana; Gómez-Barriocanal, Javier; Ramı́rez, Galo

doi:10.1016/0197-0186(84)90084-6

Cited by 25 publications

(4 citation statements)

References 16 publications

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“…Instead, class I1 A-forms are only partially sensitive to the presence of the innervation. In this context, our results support the preliminary studies of Barat et al (1984) on chicken leg muscles.…”

Section: Discussionsupporting

confidence: 93%

Nerve regulation of class I and Class II‐asymmetric forms of acetylcholinesterase in rat skeletal muscles

Fadić

Inestrosa

1989

J of Neuroscience Research

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Two classes of collagen-tailed, asymmetric forms (A-forms) of acetylcholinesterase (AChE) have been described in skeletal muscles of vertebrates. They are distinguished by their different solubilization requirements: class I A-forms are solubilized in the presence of high salt, whereas class II A-forms require in addition a chelating agent for solubilization. We report here that class II A-forms are less sensitive to nerve section than are class I A-forms. The latter form decreases faster and to a lower level of activity after denervation. The decay of both AChE classes is more rapidly in short-stump nerves than in long ones. The effect of nerve section on class II A-forms appears to be dependent on the particular muscle group being studied. Both classes of A-forms reappear after muscle reinnervation, but the class I A-forms recovered earlier. More interestingly, both classes of A-forms increase in normally innervated skeletal muscles after contralateral nerve injury. In this case, however, the class II A-forms change first. Muscular disuse induced by contralateral tenotomy is also followed by a rise in class II A-forms. Our results, showing differences in response and flexibility in the changes of the two classes of A-forms in several experimental conditions, represent a relevant contribution to the understanding of the regulation and functional role of the asymmetric forms of AChE in vertebrate skeletal muscles.

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Section: Discussionsupporting

confidence: 93%

Nerve regulation of class I and Class II‐asymmetric forms of acetylcholinesterase in rat skeletal muscles

Fadić

Inestrosa

1989

J of Neuroscience Research

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“…Furthermore, in all of our experiments, a fraction of the asymmetric enzyme remained unbound to lectin. Whether incomplete binding is simply a consequence of the conditions of our assay, or whether it represents heterogeneity within the asymmetric pool (Barat et al, 1984) remains to be determined.…”

Section: Discussionmentioning

confidence: 99%

A synapse-specific carbohydrate at the neuromuscular junction: association with both acetylcholinesterase and a glycolipid

1988

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With the aim of investigating the roles of carbohydrates in synapse formation, we have characterized a synapse-specific saccharide at the vertebrate neuromuscular junction. Two lectins of similar specificity (Dolichos biflorus agglutinin, DBA, and Vicia villosa-B4 agglutinin, VVA-B4) stain synaptic but not extrasynaptic regions of the rat muscle fiber surface and thus define a synapse-specific carbohydrate. Using these and other probes, we show that the carbohydrate moiety concentrated at the neuromuscular junction resembles N-acetylgalactosamine (GalNAc) linked in the beta-anomeric form to the termini of oligosaccharides. VVA-B4 also selectively stains neuromuscular junctions in human, mouse, rabbit, guinea pig, chick, frog, axolotl, snake, fish, and lamprey muscles, a phylogenetic conservatism that suggests a synapse-related role for GalNAc beta-terminal saccharides. AChE from muscle binds to DBA- and VVA-B4-agarose, and is thereby identified as a glycoconjugate bearing the synapse-specific carbohydrate. Assay of AChE isoforms reveals that asymmetric, collagen-tailed forms, known to be highly concentrated at the rat neuromuscular junction, bind DBA and VVA-B4, while globular forms, which are more widely distributed, do not. A second class of GalNAc-bearing glycoconjugates is demonstrable immunohistochemically with monoclonal antibodies to stage-specific embryonic antigen (SSEA)-3 (Shevinsky et al., 1982) and GM2 (Natoli et al., 1986), which recognize GalNAc-bearing glycolipids. These antibodies selectively stain neuromuscular junctions, where they recognize glycolipid-like molecules that bind VVA-B4 but are distinguishable from AChE. The association of a synapse-specific carbohydrate with at least 2 different synapse-specific molecules raises the possibility that the former plays a role in determining a property that the latter share, such as concentration at the synapse.

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“…Solubilization by heparin and heparan sulfate Brandan et a]., 1985;Barat et al, 1986) and interaction with immobilized heparin (Brandan and Inestrosa, 1984;Brandan et al, 1986) have been put forward as experimental evidence for the involvement of the GAG moiety of proteoglycans in the anchorage of asymmetric AChE species to the extracellular matrix in skeletal muscle and neural tissues. In our hands, both fractions of A-forms ("classes" or types A' and A": Barat et al, 1984;Ramirez et al, 1984) are extracted by heparin from chick muscle and retina with the same efficiency, giving rise to similar enzyme-heparin complexes sedimenting at 24s in heparin-containing sucrose gradients, and being converted to AI2 and A8 forms in 1 M salt-containing sucrose gradients (Barat et al, 1986). Heparin then circumvents the need of EDTA for solubilization of A"-forms.…”

Section: Interaction Of Asymmetric Ache Species With Heparinmentioning

confidence: 99%

“…Asymmetric forms of AChE have been classically connected with synaptic function in the peripheral cholinergic systems, in view of their association to motor end-plates and their sensitivity to denervation (Hall, 1973;Vigny et al, 1976;Barat et al, 1984;FernLndez and Stiles, 1984;FernLndez et al, 1984), much to the comparative neglect of G-forms as functionally relevant components of the cholinergic synapse. Not surprisingly, nearly every study on the anchorage of AChE to synaptic sites deals with A-forms, and especially with the enzyme collagenous tail.…”

Section: Interaction Of Globular Ache Species With Heparinmentioning

confidence: 99%

Interaction of Asymmetric and Globular Acetylcholinesterase Species with Glycosaminoglycans

Ramı́rez

Barat

Fernández

1990

Journal of Neurochemistry

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Chicken muscle and retina, and rat muscle asymmetric acetylcholinesterase (AChE) species were bound to immobilized heparin at 0.4 M NaCl. Binding efficiency was between 50 and 80% for crude fraction I A-forms (AI; muscle), and nearly 100% for fraction II A-forms (AII; muscle and retina). Antibody-affinity-purified AI-forms (chicken) were, however, quantitatively bound to heparin-agarose gels, whereas diisopropylfluorophosphate-inactivated high-salt extracts partially prevented the binding of both AI and AII AChE forms, thus suggesting the presence in crude AI extracts of heparin-like molecules interfering with the tail-heparin interaction. All bound A-forms were progressively displaced from the heparin-agarose columns by increasing salt concentrations, with maximal release at about 0.6 M. They were also efficiently eluted by heparin solutions (1 mg/ml), other glycosaminoglycans being much less effective. Chicken globular AChE forms (G-forms, both low-salt-soluble and detergent-soluble) also bound to immobilized heparin in the absence of salt. Stepwise elution with increasing NaCl concentrations showed maximal release of G-forms at 0.15 M, all globular forms being totally displaced from the column at 0.4 M NaCl. Heparin (1 mg/ml) had the same eluting capacity as 0.4 M NaCl, whereas other glycosaminoglycans were only marginally effective. We conclude that the molecular forms of AChE in these vertebrate species interact with heparin, at salt concentrations that are characteristic for asymmetric and globular forms. Within the A and G molecular form groups, no differences were found in the behavior of the different fractions or subtypes, provided that the enzyme samples were free of interfering molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

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Two classes of collagen-tailed, asymmetric molecular forms of acetylcholinesterase in skeletal muscle: differential effects of denervation

Cited by 25 publications

References 16 publications

Nerve regulation of class I and Class II‐asymmetric forms of acetylcholinesterase in rat skeletal muscles

Nerve regulation of class I and Class II‐asymmetric forms of acetylcholinesterase in rat skeletal muscles

A synapse-specific carbohydrate at the neuromuscular junction: association with both acetylcholinesterase and a glycolipid

Interaction of Asymmetric and Globular Acetylcholinesterase Species with Glycosaminoglycans

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