TY - JOUR
T1 - Primary structure, functional characterization and developmental expression of the ascidian Kv4-class potassium channel
AU - Nakajo, Koichi
AU - Katsuyama, You
AU - Ono, Fumihito
AU - Ohtsuka, Yukio
AU - Okamura, Yasushi
N1 - Funding Information:
This work is partially supported by Grants-in-Aid for JSPS Fellows and Grant-in-Aid for Creative Scientific Research from the Japanese Ministry of Education, Science and Culture of Japan and Kanehara Memorial Foundation. DDBJ accession numbers for TuKv4a and TuKv4b are AB084422 and AB084423, respectively.
PY - 2003/1/1
Y1 - 2003/1/1
N2 - Ascidians belong to the primitive chordates and their larvae show symmetrical beating of the tail, which is reminiscent of the swimming pattern in primitive vertebrates. Since ascidian larva contains only a small number of neurons in their entire larval nervous system, they will potentially provide a simple model for the study of animal locomotion. In a step towards the goal of establishing the molecular basis underlying ascidian larval neurophysiology, we describe here a Kv4 class of voltage-gated potassium channel, TuKv4, from Halocynthia roretzi. Whole mount in situ hybridization indicates that TuKv4 is expressed in most of larval neurons including motor neurons. TuKv4-currents reconstituted in Xenopus oocytes show currents with similar properties to the lower-threshold A-type currents from cleavage-arrested ascidian blastomeres of neural lineage. However, the voltage-dependency of the steady-state inactivation and activation was shifted leftward by 20 mV, as compared with native A-type currents, suggesting that other components may be required to restore full function of the Kv4 channel. Unexpectedly, another isoform lacking C-terminal cytoplasmic region was also isolated. This truncated isoform did not lead to a functional current in Xenopus oocytes. RT-PCR analysis showed that the truncated form is transiently expressed during larval development, suggesting some developmental role for potassium channel expression.
AB - Ascidians belong to the primitive chordates and their larvae show symmetrical beating of the tail, which is reminiscent of the swimming pattern in primitive vertebrates. Since ascidian larva contains only a small number of neurons in their entire larval nervous system, they will potentially provide a simple model for the study of animal locomotion. In a step towards the goal of establishing the molecular basis underlying ascidian larval neurophysiology, we describe here a Kv4 class of voltage-gated potassium channel, TuKv4, from Halocynthia roretzi. Whole mount in situ hybridization indicates that TuKv4 is expressed in most of larval neurons including motor neurons. TuKv4-currents reconstituted in Xenopus oocytes show currents with similar properties to the lower-threshold A-type currents from cleavage-arrested ascidian blastomeres of neural lineage. However, the voltage-dependency of the steady-state inactivation and activation was shifted leftward by 20 mV, as compared with native A-type currents, suggesting that other components may be required to restore full function of the Kv4 channel. Unexpectedly, another isoform lacking C-terminal cytoplasmic region was also isolated. This truncated isoform did not lead to a functional current in Xenopus oocytes. RT-PCR analysis showed that the truncated form is transiently expressed during larval development, suggesting some developmental role for potassium channel expression.
KW - Ascidian
KW - Kv4 potassium channel
KW - Locomotion
KW - Motor neuron
KW - Truncated form
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U2 - 10.1016/S0168-0102(02)00193-1
DO - 10.1016/S0168-0102(02)00193-1
M3 - Article
C2 - 12507725
AN - SCOPUS:0037219037
SN - 0168-0102
VL - 45
SP - 59
EP - 70
JO - Neuroscience Research
JF - Neuroscience Research
IS - 1
ER -