Two Classes of Collagen-Tailed Molecular Forms of Acetylcholinesterase

Ramı́rez, Galo; Gómez-Barriocanal, Javier; Barat, Ana; Rodríguez-Borrajo, Corona

doi:10.1515/9783110848496-012

Cited by 13 publications

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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%

“…linergic tissues and species Brandan et al, 1985; Barat et al, 1986), and by t h e interaction between tailed A C h E and immobilized heparin (Brandan a n d Inestrosa, 1984; Brandan et al, 1986). The fact that globular A C h E forms (G-forms) have not been considered in these studies, in spite of their possible localization in basal laminae a t t h e vertebrate neuromuscular junction (Jedrejczyk et al, 1984;Nicolet et al, 1986Nicolet et al, , 1987, and some contradictions exist between different laboratories concerning the relative affinity for heparin o f two fractions (I and 11, A' and A", also referred to, i n previous papers, as "classes" or "types") of A-forms with different solubility properties (Barat e t al., 1984(Barat e t al., , 1986Ramirez et al, 1984;Brandan et al, 1986), have prompted us to reexamine the interaction of the different molecular forms of t h e enzyme with immobilized heparin, and t h e effects of different glycosaminoglycans (GAGs) thereupon.…”

Section: I761 I762mentioning

confidence: 99%

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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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Section: Interaction Of Asymmetric Ache Species With Heparinmentioning

confidence: 99%

Section: I761 I762mentioning

confidence: 99%

Interaction of Asymmetric and Globular Acetylcholinesterase Species with Glycosaminoglycans

Ramı́rez

Barat

Fernández

1990

Journal of Neurochemistry

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“…As in many other neural structures with a cholinergic component, chick retina contains both asymmetric (A-forms) and globular (G-forms) AChE isoenzymes. Chick retinal A-forms belong to the so-called type I1 species Ramirez et al, 1984), requiring both high ionic strength and chelating agents for solubilization G6mez-Barriocanal et al, 1981G6mez-Barriocanal et al, , 0 1989 Alan R. Liss, Inc. 1983). In turn, chick retinal G-forms are mainly of the detergent-soluble type (MassouliC and Bon, 1982).…”

Section: Introductionmentioning

confidence: 99%

Compartmentalization of acetylcholinesterase in the chick retina

Ramı́rez¹,

Barat²,

Donoso³

et al. 1989

J of Neuroscience Research

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Using selective inhibitor treatments, we have studied the distribution of asymmetric (A) and globular (G) forms of acetylcholinesterase (AChE) in the extra- and intracellular compartments of chick retina, a specialized region of chick central nervous system (CNS). Our results show that the chick retinal collagen-tailed AChE (an example of class II asymmetric molecular forms) is essentially an extracellular form of the enzyme; this is the first demonstration of the extracellular localization of asymmetric AChE in the vertebrate CNS. The active site of most of the hydrophobic, membrane-bound G4-form is also exposed to the external environment. In turn, the smaller molecular weight G-forms (G2 and G1) are localized within the cells, where they may represent intermediate components in the assembly or degradation of the more complex enzymatic molecular species. Histoenzymatic ultrastructural techniques show internal AChE in amacrine as well as in ganglion cell bodies, and external enzyme, specifically associated with synapses and axons, in the inner plexiform layer. The probable cooperation of the extracellular A12-forms and the membrane-bound G species (mainly G4) of the enzyme to the hydrolysis of acetylcholine (ACh) released into the external compartment is suggested and discussed.

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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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Two Classes of Collagen-Tailed Molecular Forms of Acetylcholinesterase

Cited by 13 publications

References 0 publications

Interaction of Asymmetric and Globular Acetylcholinesterase Species with Glycosaminoglycans

Interaction of Asymmetric and Globular Acetylcholinesterase Species with Glycosaminoglycans

Compartmentalization of acetylcholinesterase in the chick retina

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

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