Internal Ca2+ mobilization is altered in fibroblasts from patients with Alzheimer disease.

Abstract

The recent demonstration of K+ channel dysfunction in fibroblasts from Alzheimer disease (AD) patients and past observations of Ca2+-mediated K+ channel modulation during memory storage suggested that AD, which is characterized by memory loss and other cognitive deficits, might also involve dysfunction of intracellular Ca2+ mobilization. Bombesin-induced Ca2+ release, which is inositol trisphosphate-mediated, is shown here to be greatly enhanced in AD fibroblasts compared with fibroblasts from control groups. Bradykinin, another activator of phospholipase C, elicits similar enhancement of Ca2+ signaling in AD fibroblasts. By contrast, thapsigargin, an agent that releases Ca2+ by direct action on the endoplasmic reticulum, produced no differences in Ca2+ increase between AD and control fibroblasts. Depolarization-induced Ca2+ influx data previously demonstrated the absence of between-group differences of Ca2+ pumping and/or buffering. There was no correlation between the number of passages in tissue culture and the observed Ca2+ responses. Furthermore, cells of all groups were seeded and analyzed at the same densities. Radioligand binding experiments indicated that the number and affinity of bombesin receptors cannot explain the observed differences. These and previous observations suggest that the differences in bombesin and bradykinin responses in fibroblasts and perhaps other cell types are likely to be due to alteration of inositol trisphosphatemediated release of intracellular Ca2+.A number of cellular changes have been observed in fibroblasts from patients with Alzheimer disease (AD). These include abnormality of glucose and energy-related metabolism (1), defective release of a cholinergic factor (2), abnormal f8-amyloid expression and processing (3), changes in Ca2+ metabolism (30-34), and altered p-adrenergic-induced cAMP formation (4). The recent demonstration of K+ channel dysfunction in AD fibroblasts (5, 6) and past observations of Ca2+-mediated K+ channel modulation during memory storage (7) suggested that AD, which is characterized by memory loss and other cognitive deficits (8, 9), might also involve dysfunction of intracellular Ca2+ mobilization. Bombesin (10-12), an agent that activates phospholipase C (PLC) to generate inositol 1,4,5-trisphosphate (1P3) (13)(14)(15) different for AD and control fibroblasts. f-Amyloid protein (23-25) itself, while causing the previously observed inactivation of K+ channels in AD fibroblasts, had no effect on the bombesin-elicited Ca2+ signals. These and other findings, together with measurements of bombesin receptor number, suggest that PLC/G-protein coupling and/or IP3 receptors are responsible for differences in Ca2+ responses between AD and non-AD fibroblasts. METHODSCell Lines. Human skin fibroblasts (Table 1) were purchased from the Coriell Cell Repositories (Camden, NJ). Cells were seeded and maintained as described (5). The number of passages was not significantly different between groups [AD, 10.9 ± 1.3 (mean ± SEM), n = 10; AC, 11.5 + 0.8, n = 8;...

Calcium Homeostasis and Reactive Oxygen Species Production in Cells Transformed by Mitochondria from Individuals with Sporadic Alzheimer’s Disease

“…AD fibroblasts have an increased cytosolic calcium response to InsP 3 formation agonists (Peterson et al, , 1988Huang et al, 1991;McCoy et al, 1993;Etcheberrigaray et al, 1994;Ito et al, 1994). These reports are consistent with enhancement of InsP 3 -mediated calcium release in AD cybrids.…”

Subcellular Mechanisms of Presenilin-Mediated Enhancement of Calcium Signaling

“…Like effects on APP processing, calcium signaling alterations appear to be an early and invariant consequence of presenilin mutations, having been documented for multiple mutations in PS1 and PS2 in numerous experimental systems (Barrow et al, 2000;Etcheberrigaray et al, 1998;Gibson et al, 1996;Hirashima et al, 1996;Ito et al, 1994;Keller et al, 1998;Leissring et al, 2000a;Leissring et al, 1999a;Leissring et al, 1999bLeissring et al, , 2000bMattson et al, 2000b;Parent et al, 1999). For instance, even prior to the identification of the presenilins, calcium alterations were described in skin fibroblasts from a family of chromosome 14-linked FAD patients, who were later shown to harbor the A246Q mutation in PS1 (Ito et al, 1994).…”

“…For instance, even prior to the identification of the presenilins, calcium alterations were described in skin fibroblasts from a family of chromosome 14-linked FAD patients, who were later shown to harbor the A246Q mutation in PS1 (Ito et al, 1994). Intriguingly, these perturbations in calcium signaling are so selective and so consistent that they can be used to reliably predict FAD several years prior to presentation of overt neurological symptoms (Etcheberrigaray et al, 1998).…”

“…The specific constellation of disturbances conferred by presenilin mutations include (i) a potentiation of calcium release from the ER (Etcheberrigaray et al, 1998;Gibson et al, 1996;Ito et al, 1994;Leissring et al, 2000aLeissring et al, , 1999aLeissring et al, , 1999bLeissring et al, , 2000b and (ii) deficits in capacitative calcium entry (CCE; Leissring et al, 2000a;Yoo et al, 2000), an important signaling pathway wherein depletion of ER calcium stores triggers a sustained influx of extracellular calcium into the cytosol (Berridge, 1995). Although these alterations are now well described, and have proven diagnostic utility (Etcheberrigaray et al, 1998), the mechanisms underlying these changes are poorly understood.…”

“…Studies on the effects of presenilin mutations on calcium signaling have predominantly focused on the phosphoinositide signal transduction pathway, in which calcium is liberated from the ER into the cytosol through receptor/channel complexes activated by the second messenger inositol 1,4,5-trisphosphate (IP 3 ; Etcheberrigaray et al, 1998;Gibson et al, 1996;Ito et al, 1994;Leissring et al, 2000a). The specific constellation of disturbances conferred by presenilin mutations include (i) a potentiation of calcium release from the ER (Etcheberrigaray et al, 1998;Gibson et al, 1996;Ito et al, 1994;Leissring et al, 2000aLeissring et al, , 1999aLeissring et al, , 1999bLeissring et al, , 2000b and (ii) deficits in capacitative calcium entry (CCE; Leissring et al, 2000a;Yoo et al, 2000), an important signaling pathway wherein depletion of ER calcium stores triggers a sustained influx of extracellular calcium into the cytosol (Berridge, 1995).…”