Effects of Amyloid-beta Peptides on Voltage-Gated L-Type Ca(V)1.2 and Ca(V)1.3 Ca2+ Channels

Abstract

Overload of intracellular Ca2+ has been implicated in the pathogenesis of neuronal disorders, such as Alzheimer's disease. Various mechanisms produce abnormalities in intracellular Ca2+ homeostasis systems. L-type Ca2+ channels have been known to be closely involved in the mechanisms underlying the neurodegenerative properties of amyloid-beta (A beta) peptides. However, most studies of L-type Ca2+ channels in A beta-related mechanisms have been limited to Ca(V)1.2, and surprisingly little is known about the involvement of Ca(V)1.3 in A beta-induced neuronal toxicity. In the present study, we examined the expression patterns of Ca(V)1.3 after A beta(25-35) exposure for 24 h and compared them with the expression patterns of Ca(V)1.2. The expression levels of Ca(V)1.3 were not significantly changed by A beta(25-35) at both the mRNA levels and the total protein level in cultured hippocampal neurons. However, surface protein levels of Ca(V)1.3 were significantly increased by A beta(25-35), but not by A beta(35-25). We next found that acute treatment with A beta(25-35) increased Ca(V)1.3 channel activities in HEK293 cells using whole-cell patch-clamp recordings. Furthermore, using GTP pulldown and co-immunoprecipitation assays in HEK293 cell lysates, we found that amyloid precursor protein interacts with beta(3) subunits of Ca2+ channels instead of Ca(V)1.2 or Ca(V)1.3 alpha(1) subunits. These results show that A beta(25-35) chronically or acutely upregulates Ca(V)1.3 in the rat hippocampal and human kidney cells (HEK293). This suggests that Ca(V)1.3 has a potential role along with Ca(V)1.2 in the pathogenesis of Alzheimer's disease.