Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.16 (calcineurin)
 17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A stable CHO-K1 cell line was developed which expresses the human small conductance calcium-activated potassium channel hSK3. Immunofluorescence microscopy using an anti-SK3 antibody and radioligand binding using [(125)I]-apamin demonstrated the presence of hSK3 channel in the recombinant cell line. This cell line was utilised in a fluorescence assay using the membrane potential-sensitive dye DiBAC(4)(3) to functionally analyse and pharmacologically characterise this potassium channel. The analysis of known blockers of calcium-activated potassium channels revealed the highest potency for apamin (IC(50)=13.2 nM). This result was confirmed by direct recordings of SK3 currents using the whole-cell patch-clamp technique. Tricyclic antidepressants such as desipramine, imipramine and nortriptyline as well as phenothiazines such as fluphenazine, promethazine, chlorpromazine and trifluoperazine blocked the hSK3 channel with micromolar potencies. These compounds also displaced [(125)I]-apamin binding to the hSK3 channel thus suggesting direct and competitive channel blocking activity. Since these compounds share a common three-ring molecular core structure, this feature seems to be important for channel blocking activity. The serine/threonine protein phosphatase inhibitors okadaic acid and calyculin A were able to abolish channel activation with nanomolar potencies, but did not displace [(125)I]-apamin binding. Thus, phosphorylation of hSK3 or an accessory channel subunit seems to be involved in its modulation.
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PMID:Pharmacological characterisation of the human small conductance calcium-activated potassium channel hSK3 reveals sensitivity to tricyclic antidepressants and antipsychotic phenothiazines. 1136 31

Dopaminergic (DA) neurons in substantia nigra pars compacta (SNc) are vulnerable to excitotoxicity in Parkinson's disease (PD). Neurotoxic stimuli may alter the firing patterns of DA neurons. However, whether firing pattern change underlies neurotoxic stress-induced death of DA neurons remains unknown. In this study, we established long-term cultures of SNc organotypic slices and used this model to evaluate the neurotoxic effects on firing mode and DA neuronal viability following chronic treatment with neurotoxin 6-hydroxydopamine (6-OHDA). Using whole-cell patch clamp to explore the intrinsic membrane properties and firing mode, we showed that chronic exposure to 6-OHDA raised the resting membrane potential of SNc DA neurons and altered their firing pattern, causing it to switch from a regular rhythmic pacemaking firing to an irregular bursting. This firing pattern change correlated with increased death of SNc DA neurons. The 6-OHDA-induced firing pattern change correlated with an increase in the activity of the small conductance calcium-activated potassium channel (SK channel) and with an increase in both the level and activity of protein phosphatase 2A (PP2A). Activation of the SK channel by its agonist 1-EBIO attenuated 6-OHDA-induced firing irregularity and death, while the SK channel antagonist apamin exacerbated the toxic effects of 6-OHDA. Thus, SK channel current is a substantial element in sustaining the SNc DA neuronal rhythmic pacemaking and homeostasis and perturbing SK channel activity underlies 6-OHDA-induced neurotoxicity.
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PMID:Firing pattern modulation through SK channel current increase underlies neuronal survival in an organotypic slice model of Parkinson's disease. 2484 82