Jeong Sung-kwon

Modulation of the activity of potassium and other ion channels is an essential feature of nervous system function. The open probability of a large conductance Ca(2+)-activated K+ channel from rat brain, incorporated into planar lipid bilayers, is increased by the addition of adenosine triphosphate (ATP) to the cytoplasmic side of the channel. This modulation takes place without the addition of protein kinase, requires Mg2+, and is mimicked by an ATP analog that serves as a substrate for protein

Amyloid-β protein precursor (AβPP) is transported to the plasma membrane, where it is sequentially cleaved by α-secretase and γ-secretase. This is called non-amyloidogenic pathway since it precludes the production of amyloid-β (Aβ), the main culprit of Alzheimer's disease (AD). Alternatively, once AβPP undergoes clathrin-dependent endocytosis, it can be sequentially cleaved by β-secretase and γ-secretase at endosomes, producing Aβ (amyloidogenic pathway). β-N-acetylglucosamine (GlcNAc) can be at

Familial Alzheimer's disease (FAD)-associated presenilin 1 (PS1) serves as a catalytic subunit of γ-secretase complex, which mediates the proteolytic liberation of β-amyloid (Aβ) from β-amyloid precursor protein (APP). In addition to its proteolytic role, PS1 is involved in non-proteolytic functions such as protein trafficking and ion channel regulation. Furthermore, postmortem AD brains as well as AD patients showed dysregulation of cholesterol metabolism. Since cholesterol has been implicated

Amyloid precursor protein (APP) at the plasma membrane is internalized via endocytosis and delivered to endo/lysosomes, where neurotoxic amyloid-β (Aβ) is produced via β-, γ-secretases. Hence, endocytosis plays a key role in the processing of APP and subsequent Aβ generation. β-, γ-secretases as well as APP are localized in cholesterol-enriched lipid raft microdomains. However, it is still unclear whether lipid rafts are the site where APP undergoes endocytosis and whether cholesterol levels aff

Amyloid β-peptide (Aβ) pathology is an invariant feature of Alzheimer disease, preceding any detectable clinical symptoms by more than a decade. To this end, we seek to identify agents that can reduce Aβ levels in the brain via novel mechanisms. We found that (20 S )-Rg3, a triterpene natural compound known as ginsenoside, reduced Aβ levels in cultured primary neurons and in the brains of a mouse model of Alzheimer disease. The (20 S )-Rg3 treatment induced a decrease in the association of prese

We measured the activity of the Ca(2+) release-activated Ca(2+) (CRAC) channel present in cultured rat microglia, using the whole-cell mode of patch clamp technique. When the concentration of divalent cations in external solution was reduced to the micromolar range, and Ca(2+) chelating agent BAPTA was included in the pipette solution, we were able to record Na(+) current through CRAC channels in single-channel levels. The unitary Na(+) conductance through CRAC channel was 42.5 pS, which was sim

The clonal rat pituitary cell line GH4C1 expresses the genes for several voltage-dependent potassium channels including Kv1.5 and Kv1.4. Dexamethasone, a glucocorticoid agonist, induces a slowly inactivating potassium current in these cells but does not alter the amplitude of a rapidly inactivating component of potassium current. We have found that the induction of the slowly inactivating current can be blocked by an antisense phosphorothioate deoxyoligonucleotide to the Kv1.5 mRNA sequence. In

Modulation of voltage-dependent potassium currents can alter the shape and timing of action potentials, thereby altering neurotransmitter release. To examine the effect of a cAMP analog on potassium currents in metabolically intact cells, perforated-patch and cell-attached patch recordings were carried out using the GH4C1 pituitary cell line. A major component of voltage-dependent potassium current in these cells inactivates slowly, with a time constant of several seconds. Application of dibutyr

Presenilins (PS1 and PS2) are multifunctional proteins involved in a diverse array of molecular and cellular functions, including proteolysis, development, neurogenesis, synaptic plasticity, ion channel regulation and phospholipid metabolism. Mutations in presenilin genes are responsible for the majority of Familial Alzheimer disease (FAD). Consequently, FAD-associated mutations in genes encoding PS1 or PS2 lead to several key cellular phenotypes, including alterations in proteolysis of β-amyloi