Reciprocal modulation between amyloid precursor protein and synaptic membrane cholesterol revealed by live cell imaging.

The amyloid precursor protein (APP) has been extensively studied because of its association with Alzheimer's disease (AD). However, APP distribution across different subcellular membrane compartments and its function in neurons remains unclear. We generated an APP fusion protein with a pH-sensitive green fluorescent protein at its ectodomain and a pH-insensitive blue fluorescent protein at its cytosolic domain and used it to measure APP's distribution, subcellular trafficking, and cleavage in live neurons.

The Fate of Nascent APP in Hippocampal Neurons: A Live Cell Imaging Study.

Amyloid precursor protein (APP) is closely associated with Alzheimer's disease (AD) because its proteolytic products form amyloid plaques and its mutations are linked to familial AD patients. As a membrane protein, APP is involved in neuronal development and plasticity. However, it remains unclear how nascent APP is distributed and transported to designated membrane compartments to execute its diverse functions.

Fluorescent Measurement of Synaptic Activity Using FM Dyes in Dissociated Hippocampal Cultured Neurons.

Release and recycling of synaptic vesicles are essential for neurotransmission and synaptic plasticity. To gain mechanistic understanding of these processes, direct measurements of vesicle release and retrieval is indispensable. Styryl dyes like FM1-43 and FM4-64 have been widely used for this purpose and their loading and unloading are reliable measurements for synaptic vesicle release and retrieval in cultured neurons.

Ammonium chloride alters neuronal excitability and synaptic vesicle release.

Genetically encoded pH-sensors are widely used in studying cell membrane trafficking and membrane protein turnover because they render exo-/endocytosis-associated pH changes to fluorescent signals. For imaging and analysis purposes, high concentration ammonium chloride is routinely used to alkalize intracellular membrane compartments under the assumption that it does not cause long-term effects on cellular processes being studied like neurotransmission. However, pathological studies about hyperammonemia have shown that ammonium is toxic to brain cells especially astrocytes and neurons.

Two amino acid sequences direct Aspergillus nidulans protein kinase C (PkcA) localization to hyphal apices and septation sites.

The Aspergillus nidulans ortholog of protein kinase C (pkcA) is involved in the organism's putative cell wall integrity (CWI) pathway, and PkcA also is highly localized at growing tips and forming septa. In the present work we identify the regions within PkcA that are responsible for its localization to hyphal tips and septation sites. To this end, we used serially truncated pkcA constructs and expressed them as green fluorescent protein (GFP) chimeras and identified two regions that direct PkcA localization.