Research article

Expression of ryanodine receptors in human embryonic kidney (HEK293) cells

Henry W. QUERFURTH, Norman J. HAUGHEY, Steven C. GREENWAY, Patrick W. YACONO, David E. GOLAN, Jonathan D. GEIGER


It has been shown previously that mobilization of caffeine-sensitive intracellular calcium (Ca2+i) stores increased the release of amyloid β-peptide (Aβ) from transfected human embryonic kidney cells (HEK293) [Querfurth, Jiang, Geiger and Selkoe (1997) J. Neurochem. 69, 1580–1591]. The present study was to test the hypothesis that the caffeine/Aβ responses were due to interactions with specific subtypes of ryanodine receptors (RyR) using [3H]ryanodine receptor binding, epifluorescence imaging of Ca2+i, immunocytofluorescence, immunoprecipitation and PCR techniques. [3H]Ryanodine bound to a single class of high-affinity caffeine-sensitive sites (Kd = 9.9±1.6 nM, Bmax = 25±4 fmol/mg of protein). RyRs were immuno-decorated in a punctate reticulo-linear pattern. Results from SDS/PAGE and reverse transcriptase-PCR demonstrated endogenous expression of type 1 (skeletal) and type 2 (cardiac) RyRs. HEK293 cell RyRs were functionally active, because (i) [Ca2+]i increased 2.8-fold over baseline following applications of 5–15 mM caffeine, (ii) repetitive spiked increases in [Ca2+]i were observed, and (iii) evidence for a use-dependent block was obtained. Some of these findings were extended to include HeLa and human fibroblast cell lines, suggesting a broader applicability to cells of epithelioid lineage. Implications for the processing of the β-amyloid precursor protein in Alzheimer's disease and for calcium channel research using transfected HEK293 cells are discussed.