Super-resolution microscopy reveals gamma-secretase at both sides of the neuronal synapse

• The transmembrane protein assembly gamma-secretase is a key protease in regulated intramembrane processing (RIP) of around 100 type-1 transmembrane proteins. Importantly, it has a pathological role in Alzheimer disease (AD) as it generates the neurotoxic amyloid beta-peptide from the amyloid precursor protein (APP). Studies on gamma-secretase location are therefore crucial both from a biological and a therapeutic perspective. Despite several years of efforts in many laboratories, it is not clear where in the neuron gamma-secretase exerts it's activities. Technical challenges include the fact that the active enzyme contains four protein components and that most subcellular compartments cannot be spatially resolved by traditional light microscopy. Here, we have used a powerful combination of the two nanoscopy techniques STORM and STED microscopy to visualize the location of gamma-secretase in neurons using an active-site specific probe, with a focus on the synapse. We show that gamma-secretase is present in both the pre-and postsynaptic compartments. We further show that the enzyme is enriched very close to the synaptic cleft in the postsynaptic membrane, as well as to NMDA receptors, demonstrating that gamma-secretase is present in the postsynaptic plasma membrane. Importantly, the expression of gamma-secretase increased in the pre-and postsynaptic compartments with the size of the synapse, suggesting a correlation between gamma-secretase activity and synapse maturation. Thus, our data shows the synaptic location with high precision in three dimensions and settles the long-lasting debate on the synaptic location of gamma-secretase.

Ämnesord

NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

Nyckelord

Alzheimer disease

gamma-Secretase

Synapse

Hippocampal neuron

Super-resolution microscopy

Stimulated emission depletion (STED) microscopy

Stochastic optical resolution microscopy (STORM)

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