Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum

Franco, Rafael; Canela, Enric I.; Bozal, J.

doi:10.1007/bf00965016

Cited by 66 publications

(32 citation statements)

References 31 publications

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“…ADA from calf intestine (Roche Diagnostics) was desalted by passage through a PD-10 column (Amersham Pharmacia), and its enzymatic activity was tested. Enzymatic activity of ADA was evaluated by measuring the decrease of absorbance at 265 nm (28). To obtain ADA without enzymatic activity, desalted ADA was treated with HgCl 2 as described in ref.…”

Section: Methodsmentioning

confidence: 99%

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

Pacheco

Martinez-Navío

Lejeune

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

221

192

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Adenosine deaminase (ADA), a protein whose deficit leads to severe combined immunodeficiency, binds to the cell surface by means of either CD26, A 1 adenosine receptors, or A2B adenosine receptors. The physiological role of these interactions is not well understood. Our results show that by a 3-fold reduction in the EC 50 for the antigen, ADA potentiated T cell proliferation in autologous cocultures with antigen-pulsed immature or mature dendritic cells. Costimulation was not due to the enzymatic activity but to the interaction of ADA-CD26 complexes in T cells with an ADAanchoring protein in dendritic cells. From colocalization studies, it is deduced that ADA colocalizing with adenosine receptors on dendritic cells interact with CD26 expressed on lymphocytes. This costimulatory signal in the immunological synapse leads to a marked increase (3-to 34-fold) in the production of the T helper 1 and proimmflamatory cytokines IFN-␥, TNF-␣, and IL-6. adenosine deaminase ͉ costimulation ͉ immunosynapse A denosine deaminase (ADA; EC 3.5.4.4) an enzyme involved in purine metabolism, catalyzes the hydrolytic deamination of adenosine or 2Ј-deoxyadenosine to inosine or 2Ј-deoxyinosine and ammonia. Congenital defect of ADA causes severe combined immunodeficiency, which is characterized by the absence of functional T and B lymphocytes in affected individuals (1). For many years, ADA was considered to be cytosolic, but it has been found on the cell surface of many cell types; therefore, it can be considered an ectoenzyme. In addition, ecto-ADA has been proposed to have a catalytic-independent function as a costimulatory molecule in lymphocytes (2).So far, two types of surface anchoring proteins for ecto-ADA have been described. The first type, with only one member, is CD26, a multifunctional protein of 110 KDa strongly expressed on epithelial cells (kidney proximal tubules, intestine, and bile duct) and on several types of endothelial cells and fibroblasts and on leukocyte subsets (3-5). The second type of ecto-ADA-binding proteins includes the adenosine receptors (AR) A 1 (A 1 R) (6) and A 2B (A 2B R) (7). The association between ADA and CD26 on the T cell surface has been proposed to have a costimulatory function during T cell antigen receptor-CD3 complex engagement (2). Because CD26 has a short cytoplasmatic tail, it needs partners to transduce the signal. Ishii et al. (8) have described that CD26-mediated signaling occurs through its association with CD45RO. At present, it is not known whether ADA generates a signal when it binds to AR. However, we have previously demonstrated that ADA binding to A 1 R or A 2B R is required for high efficiency affinity binding of the agonist and for efficient agonist-dependent signaling (6, 7).Dendritic cells (DC) are the most potent antigen-presenting cells (APC) specialized in the initiation of immune responses by directing the activation and differentiation of naïve T lymphocytes (9, 10). Immature DC (iDC) reside in most tissues to uptake antigen; they are engaged when exposed to danger ...

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Section: Methodsmentioning

confidence: 99%

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

Pacheco

Martinez-Navío

Lejeune

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

221

192

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“…Adenosine deaminase (ADA, EC 4.5.4.4) and lactate dehydrogenase (EC 1.1.1.29) activities were estimated as described by Franco et al [11] (in the presence of 1 pM dipyridamole and 1 pM nitrobenzylthioinosine as adenosine transport inhibitors). Dipeptidylpeptidase IV (CD26, EC 3.4.14.5) activity was assayed as described by Nagatsu et al [12].…”

Section: Enzyme Activities and Ada Inhibition By Hg 2+mentioning

confidence: 99%

Adenosine deaminase affects ligand‐induced signalling by interacting with cell surface adenosine receptors

et al. 1996

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Adenosine deaminase (ADA) is not only a cytosolic enzyme but can be found as an ecto-enzyme. At the plasma membrane, an adenosine deaminase binding protein (CD26, also known as dipeptidylpeptidase IV) has been identified but the functional role of this ADMCD26 complex is unclear. Here by confocal microscopy, affinity chromatography and coprecipitation experiments we show that A 1 adenosine receptor (AIR) is a second ecto-ADA binding protein. Binding of ADA to AtR increased its affinity for the ligand thus suggesting that ADA was needed for an effective coupling between A~R and heterotrimeric G proteins. This was confirmed by the fact that ASA, independently of its catalytic behaviour, enhanced the ligand-induced second messenger production via AtR. These findings demonstrate that, apart from the cleavage of adenosine, a further role of ecto-adenosine deaminase on the cell surface is to facilitate the signal transduction via AIR.

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“…ADA activity was measured as described by Franco et al (1986). Inhibition of Sephadex G-25-desalted ADA was performed by a 1-h incubation with 300 p.M HgCl2 per unit of enzyme.…”

Section: Enzyme Activity Determination and Enzyme Inhibitionmentioning

confidence: 99%

Regulation of L‐Type Calcium Channels in GH₄ Cells via A₁ Adenosine Receptors

Zapata

Navarro

Canela

et al. 1997

Journal of Neurochemistry

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Identification of A1 adenosine receptors (A1 Ps) in a tumor cell line derived from rat pituitary (GH4 ce~is) was performed by ligand binding and immunological experiments. Subsequently, the involvement of A1Rs in the regulation of calcium conductance was studied in these cells. The agonist N 6-(R) -(2-phenylisopropyl) adenosine (R-PIA) did not modify the intracellular calcium basal levels, whereas it inhibited the increase produced by 15mM KCI depolarization. The antagonist 1 ,3-dipropyl-8-cyclopentylxanthine led to the opening of voltage-dependent cell surface calcium channels in the absence of exogenous KCI. The channels were of the L type because the effect was abolished by calciseptine and by verapamil. These results suggest that endogenous adenosine exerts a tonic inhibitory effect on calcium transport. This was confirmed by the high adenosine concentration found in cell supernatants (up to 1 pM) and by the calcium mobilization produced by exogenously added adenosine deaminase. In depolarizing conditions, the calcium peak in the presence of adenosine deaminase was reduced when cells were preincubated with R-PIA, thus suggesting that A 1R activation regulates the intensity of depolarization. These results demonstrate that adenosine is an important regulator of the physiological state of pituitary tumor cells by modulating, in an autocrine manner, the activity of Ltype voltage-dependent calcium channels.

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Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum

Cited by 66 publications

References 31 publications

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

Adenosine deaminase affects ligand‐induced signalling by interacting with cell surface adenosine receptors

Regulation of L‐Type Calcium Channels in GH₄ Cells via A₁ Adenosine Receptors

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Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum

Cited by 66 publications

References 31 publications

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

CD26, adenosine deaminase, and adenosine receptors mediate costimulatory signals in the immunological synapse

Adenosine deaminase affects ligand‐induced signalling by interacting with cell surface adenosine receptors

Regulation of L‐Type Calcium Channels in GH4 Cells via A1 Adenosine Receptors

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Regulation of L‐Type Calcium Channels in GH₄ Cells via A₁ Adenosine Receptors