Compartmentalization of acetylcholinesterase in the chick retina

Abstract

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.

Extracellular and asymmetric forms of acetylcholinesterase are expressed on cholinergic and noncholinergic terminal neuropil of the developing chick retina

“…An electron-microscopic investigation of the AChE associated with these two cell types, in the presence or absence of selective AChE inhibitors that differentiate between extracellular and intracellular AChE, has given similar results (Ramirez et al 1989). In the same study, 53% of the total AChE has been estimated as having its catalytic site exposed to the extracellular compartment.…”

“…Thus, asymmetric forms typically are cell-externally exposed. They have been found at neuromuscular synapses, in the electric organ of marine rays (Massoulié and Bon 1982), but also in central nervous tissue including chick retina (Villafruela et al 1980(Villafruela et al , 1981Ramirez et al 1989), although their precise tissue distribution during development has not been determined. In the IPL of all vertebrate species, several AChE-positive subbands have been described (reviews in Marc 1986;Hutchins 1987), the first of which in the chick is detectable not long after the appearance of a morphological IPL (Layer 1983).…”

Acetyl‐ and butyrylcholinesterase activities in the rat retina and retinal pigment epithelium

“…GIA and G,A AChE forms are preferentially located inside ganglion and amacrine cells bodies and their processes in chick retina (Ramirez et al, 1989).…”

Immunocytochemical Analysis of Glycogen Phosphorylase Isozymes in the Developing and Adult Retina of the Domestic Chicken (Gallus domesticus)

“…The amacrine, ganglion and horizontal cell specific monoclonal Pax-6 antibodies and Islet-1 antibodies [39][40][41][42], were purchased from Developmental Studies Hybridoma Bank (DSHB), University of Iowa, USA. The monoclonal acetylcholinesterase (AChE) antibody 3D10 is specific for cholinergic amacrine, ganglion and some horizontal cells ( [43,44]; generous gift of Dr K. Tsim, Hongkong). The monoclonal PKC a antibody (Santa Cruz Biotechnology, Heidelberg, Germany) specifically recognizes rod bipolar cells and a sub-population of PKC a immunoreactive amacrine cells [45].…”