Reduced Alzheimer's Disease β-Amyloid Deposition in Transgenic Mice ExpressingS-Palmitoylation-Deficient APH1aL and Nicastrin

Abstract

Sequential cleavage of amyloid precursor protein by ␤-and ␥-secretases generates ␤-amyloid peptides (A␤), which accumulate in the brains of patients with Alzheimer's disease. We recently identified S-palmitoylation of two ␥-secretase subunits, APH1 and nicastrin. S-Palmitoylation is an essential posttranslational modification for the proper trafficking and function of many neuronal proteins. In cultured cell lines, lack of S-palmitoylation causes instability of nascent APH1 and nicastrin but does not affect ␥-secretase processing of amyloid precursor protein. To determine the importance of ␥-secretase S-palmitoylation for A␤ deposition in the brain, we generated transgenic mice coexpressing human wild-type or S-palmitoylation-deficient APH1aL and nicastrin in neurons in the forebrain. We found that lack of S-palmitoylation did not impair the ability of APH1aL and nicastrin to form enzymatically active protein complexes with endogenous presenilin 1 and PEN2 or affect the localization of ␥-secretase subunits in dendrites and axons of cortical neurons. When we crossed these mice with 85Dbo transgenic mice, which coexpress familial Alzheimer's disease-causing amyloid precursor protein and presenilin 1 variants, we found that coexpression of wild-type or mutant APH1aL and nicastrin led to marked stabilization of transgenic presenilin 1 in the brains of double-transgenic mice. Interestingly, we observed a moderate, but significant, reduction in amyloid deposits in the forebrain of mice expressing S-palmitoylation-deficient ␥-secretase subunits compared with mice overexpressing wild-type subunits, as well as a reduction in the levels of insoluble A␤ 40 -42 . These results indicate that ␥-secretase S-palmitoylation modulates A␤ deposition in the brain.

Ca2+ Influx through Store-operated Ca2+ Channels Reduces Alzheimer Disease β-Amyloid Peptide Secretion

“…The pMX-C99 -6myc plasmid has been previously described (34). Rabbit polyclonal antisera against STIM1, APP, PS1, and Flotillin-2 were previously generated in our laboratory and have been described (35)(36)(37)(38). The following antibodies were purchased: anti-Nicastrin (Santa Cruz), mAb 9E10 (ATCC), anti-protein disulfide isomerase (Stressgen), and mAb 4G8 (Covance).…”

Palmitoylation in Alzheimer⿿s disease and other neurodegenerative diseases

“…APH1aL and nicastrin in the forebrain and found that palmitoylation deficiency did not affect the ability of APH1aL, an isoform of APH-1 and nicastrin to form enzymatically active γ-secretase complexes [164]. However, interestingly, the transgenic mice co-expressing palmitoylationdeficient APH1aL and nicastrin exhibited a significant but moderate reduction of amyloid deposits in the forebrain and a lower level of insoluble Aβ, indicating a potential role of γ-secretase palmitoylation in the modulation of Aβ deposition in the brain.…”

Stanniocalcin 2 Is a Negative Modulator of Store-Operated Calcium Entry

“…Rabbit polyclonal antisera against STC2, GRP78, and flotillin-2 have been described previously (18,23,34). Rabbit antiserum CT11 reacts with the residues RFLEERP.…”