The adenosine 5',5''',P1,P4-tetraphosphate receptor is at the cell surface of heart cells

Abstract

We have previously demonstrated the existence of an adenosine 5',5"',P1,P4-tetraphosphate (Ap4A) receptor in mouse hart membrane fractions [Hilderman, R. H., Martin, M., Zimmerman, J. K., & Pivorun, E. P. (1991) J. Biol. Chem. 266, 6915-6918]. However, we did not determine the cellular localization or distribution of the receptor. In this report, the Ap4A receptor is shown to be on the cell surface of individual mouse heart cells by the following four methods: (1) intact cells show specific, saturable, and reversible binding of Ap4A; (2) monoclonal antibodies (Mabs) raised against the Ap4A receptor inhibit Ap4A binding to its receptor on intact heart cells; (3) bound Mabs are shown to be at the outer cell surface via reaction with a alkaline phosphatase conjugated goat anti-rat IgG; (4) when intact cells are labeled with the impermeable cell surface labeling reagent, (sulfosuccinimido) biotin, labeled receptor is immunoprecipitated with Mabs. Furthermore, subcellular fractionation of mouse hearts demonstrates that virtually all of the Ap4A receptor is associated with a membrane fraction with at least 77% of the active receptor on plasma membranes.

Membrane Lipid Domains Distinct from Cholesterol/Sphingomyelin-Rich Rafts Are Involved in the ABCA1-mediated Lipid Secretory Pathway

“…The different incubation conditions used had no effect on total cell [ 35 S]protein-specific activity. For selective labeling of plasma membrane proteins, fibroblasts were incubated for 30 min at 0°C with phosphate-buffered saline containing 1 mg/ml sulfo-N-hydroxysuccinimide-biotin to biotinylate cell-surface proteins (48). Cells were then solubilized in detergent, and ABCA1 was isolated by immunoprecipitation as described below.…”

The activation of P1‐ and P2‐purinoceptors in the guinea‐pig left atrium by diadenosine polyphosphates

“…This receptor, isolated from membrane fractions, has a molecular weight of 30 kDa, and is derived from a protein whose post-translational processing, involving a serine protease, yields precursors of 67, 55 and 42 kDa (Walker & Hilderman, 1993;Walker et al, 1993b;Hilderman et al, 1994). However, in intact cardiac myocytes the 42 kDa form of the receptor predominates, and it has been suggested that the conversion of the 42 kDa to the 30 kDa form is an artefact (Walker et al, 1993a). This compares with molecular sizes of 41-45 kD for various P2X1-, P2Yj-and P2Y2-(=P2U) purinoceptors (Lustig et al, 1993;Webb et al, 1993;Valera et al, 1994).…”

T4 DNA ligase synthesizes dinucleoside polyphosphates

“…Ap1A and other dinucleoside polyphosphates are present in chromaffin granules of bovine adrenal medulla [10][11][12], in synaptic terminals [13] and in human blood platelets [14]. After an appropriate stimulus they are released from these storage sites to the blood and through their interaction with some still not well defined purine receptors [15][16][17][18][19] they may modulate a variety of processes such as vascular tone [20], platelet aggregation [20,21], neurotransmission [22], cell proliferation [3,7,23], etc.…”