Effect of novel Chinese specific presenilin-1 V97L mutation on intracellular calcium homeostasis in human neuroblastoma

Abstract

Presenilin-1 (PS1) mutations caused by the PSEN1 gene mutations are the major cause of early onset familial Alzheimer’s disease (EOFAD). Two Chinesespecific EOFAD related PS1 mutations, V97L and A136G, have been found. Studies suggested that V97L mutation lead to the overexpression of Aβ42 and tau hyperphosphorylation, which are the major hallmarks of Alzheimer’s disease (AD), while properties of A136G were unclear. Since calcium dysregulation was suggested to play an important role in AD, the research project investigated if V97L and A136G mutations also lead to altered endoplasmic reticulum (ER) 〖Ca〗^(2+) regulation. SH-SY5Y cells transduced with retrovirus carrying V97L mutant or A136 mutant PSEN1 were used as the experiment models.

In Western blotting, while the PS1 expression level was unaffected in V97L mutant, the expression level was significantly lower in A136G mutant. In carbachol (CCh) perfusion experiment, V97L mutant was found to exaggerate ER 〖Ca〗^(2+) release when stimulated by higher concentration (30, 100 and 300 μM) CCh, while A136G mutant exaggerated ER Ca2+ release when stimulated by 30 μM and 300 μM CCh, but not 100 μM CCh. In 5% fetal bovine serum (FBS) perfusion experiment, both V97L and A136G mutants were found to sensitize 〖Ca〗^(2+) oscillation, which the sensitization effect of V97L was 3 folds of A136G.

The results suggested that V97L mutation exaggerates ER 〖Ca〗^(2+) release, possibly via interaction with IP3R. However the results of A136G were inconclusive and contradicting, therefore further investigation is needed.