Differential expression of kcnq2 splice variants: implications to m current function during neuronal development.
The KCNQ family of K(+) channels has been implicated in several cardiac and neurological disease pathologies. KCNQ2 (Q2) is a brain-derived gene, which in association with KCNQ3 (Q3) has been shown to provide a molecular basis for the neuronal M current. We have cloned a long (Q2L) and a short (Q2S) splice variant of the human KCNQ2 gene; these variants differ in their C-terminal tail. Northern blot analysis reveals that Q2L is preferentially expressed in differentiated neurons, whereas the Q2S transcript is prominent in fetal brain, undifferentiated neuroblastoma cells, and brain tumors. Q2L, transfected into mammalian cells, produces a slowly activating, noninactivating voltage-gated K(+) current that is blocked potently by tetraethylammonium (TEA; IC(50), 0.14 mm). Q2S on the other hand produces no measurable potassium currents. Cotransfection of Q2S with either Q2L, Q3, or Q2L/Q3 heteromultimers results in attenuation of K(+) current, the suppression being most profound for Q3. Inclusion of Q2S in the heteromultimer also positively shifts the voltage dependence of current activation and alters affinity for the TEA block, suggesting that under these conditions, some Q2S subunits incorporate into functional channels on the plasma membrane. In view of the crucial role of M currents in modulating neuronal excitability, our findings provide important insight into the functional consequences of differential expression of KCNQ2 splice variants: dampened potassium conductances in the developing brain could shape firing repertoires to provide cues for proliferation rather than differentiation.
Smith
J S
JS
Departments of Neuroscience and Enabling Science and Technology, AstraZeneca Pharmaceuticals, Wilmington, Delaware 19803, USA. jeff.smith@astrazeneca.com
Iannotti
C A
CA
Dargis
P
P
Christian
E P
EP
Aiyar
J
J
D017398:Alternative Splicing / Q000235:genetics*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D001921:Brain / Q000166:cytology / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism; D019556:COS Cells; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D003001:Cloning, Molecular; D005453:Fluorescence; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006801:Humans; D051656:KCNQ Potassium Channels; D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D019789:Tetraethylammonium / Q000494:pharmacology; D014162:Transfection
D051656:KCNQ Potassium Channels; D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human; D051659:KCNQ3 Potassium Channel; C496916:KCNQ3 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D019789:Tetraethylammonium; D011188:Potassium