The E280A presenilin mutation reduces voltage-gated sodium channel levels in neuronal cells.
BACKGROUND
Familial Alzheimer's disease (FAD) mutations in presenilin (PS) modulate PS/γ-secretase activity and therefore contribute to AD pathogenesis. Previously, we found that PS/γ-secretase cleaves voltage-gated sodium channel β2-subunits (Navβ2), releases the intracellular domain of Navβ2 (β2-ICD), and thereby, increases intracellular sodium channel α-subunit Nav1.1 levels. Here, we tested whether FAD-linked PS1 mutations modulate Navβ2 cleavages and Nav1.1 levels.


OBJECTIVE
It was the aim of this study to analyze the effects of PS1-linked FAD mutations on Navβ2 processing and Nav1.1 levels in neuronal cells.


METHODS
We first generated B104 rat neuroblastoma cells stably expressing Navβ2 and wild-type PS1 (wtPS1), PS1 with one of three FAD mutations (E280A, M146L or ΔE9), or PS1 with a non-FAD mutation (D333G). Navβ2 processing and Nav1.1 protein and mRNA levels were then analyzed by Western blot and real-time RT-PCR, respectively.


RESULTS
The FAD-linked E280A mutation significantly decreased PS/γ-secretase-mediated processing of Navβ2 as compared to wtPS1 controls, both in cells and in a cell-free system. Nav1.1 mRNA and protein levels, as well as the surface levels of Nav channel α-subunits, were also significantly reduced in PS1(E280A) cells.


CONCLUSIONS
Our data indicate that the FAD-linked PS1(E280A) mutation decreases Nav channel levels by partially inhibiting the PS/γ-secretase-mediated cleavage of Navβ2 in neuronal cells.
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Doo Yeon
DY
Kim
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Mary H
MH
Wertz
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Vivek
V
Gautam
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Carla
C
D'Avanzo
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Raja
R
Bhattacharyya
Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Dora M
DM
Kovacs
D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D009154:Mutation; D009474:Neurons / Q000378:metabolism*; D053763:Presenilins / Q000235:genetics*; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D061566:Voltage-Gated Sodium Channels / Q000235:genetics* / Q000378:metabolism*
D053763:Presenilins; D061566:Voltage-Gated Sodium Channels; D053829:Amyloid Precursor Protein Secretases