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The Journal of Neuroscience, February 15, 2001, 21(4):1096-1103
Differential Expression of KCNQ2 Splice Variants: Implications
to M Current Function during Neuronal Development
Jeffrey S.
Smith1,
Claudia A.
Iannotti2,
Pauline
Dargis1,
Edward P.
Christian1, and
Jayashree
Aiyar3
Departments of 1 Neuroscience and
2 Enabling Science and Technology, AstraZeneca
Pharmaceuticals, Wilmington, Delaware 19803, and
3 Merck Research Laboratories, La Jolla, California 92037
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; IC50, 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.
Key words:
K+ channel; M current; KCNQ2; KCNQ3; cloning; splice variants; patch clamp; neuronal development; ER
retention motif; RXR(R)
Copyright © 2001 Society for Neuroscience 0270-6474/01/2141096-08$05.00/0
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