KCNQ channels: Interaction with calmodulin and functional study in Drosophila.

Format:

Book

Thesis/Dissertation

Author/Creator:

Wen, Hua.

Contributor:

Levitan, Irwin B., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Neurosciences.

0317.

Penn dissertations--Neuroscience.

Neuroscience--Penn dissertations.

Local Subjects:

Penn dissertations--Neuroscience.

Neuroscience--Penn dissertations.

0317.

Physical Description:

133 pages

Contained In:

Dissertation Abstracts International 63-05B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

Calmodulin (CaM) was identified as a KCNQ2 and KCNQ3 potassium channel-binding protein, using a yeast two-hybrid screen. CaM is tethered constitutively to the channel in transfected cells, and also coimmunoprecipitates with KCNQ2/3 from mouse brain. The structural elements critical for CaM binding to KCNQ2 lie in two conserved motifs in the proximal half of the channel C-terminal domain. Truncations and point mutations in these two motifs disrupt the interaction. The voltage-dependent activation of the KCNQ2/3 channel shows no Ca 2+-sensitivity, nor is it affected by over-expression of the Ca 2+-insensitive CaM mutant. On the other hand, KCNQ2 mutants deficient in CaM binding are unable to generate detectable currents when coexpressed with KCNQ3 in CHO cells, although they are expressed and targeted to the cell membrane and retain the ability to assemble with KCNQ3. A fusion protein containing both of the KCNQ2 CaM-binding motifs competes with the full-length KCNQ2 channel for CaM binding, and decreases KCNQ2/3 current density in CHO cells. The correlation of CaM binding with channel function suggests that CaM is an auxiliary subunit of the KCNQ2/3 channel.

dQ2 was cloned from Drosophila cDNA based on its sequence homology to the mammalian channels, and represents the only KCNQ-related channel in flies. Upon expression in CHO cells, dQ2 produces a non-inactivating current that has slow kinetics and a low voltage threshold for activation. Immunocytochemistry shows that dQ2 is located in the central nervous system in late embryos, and continues to be expressed in CNS and in most of the nerve fibers in the larval stage. Several mutant fly lines with deletions in dQ2 coding regions were generated using genetic approaches. Analysis of mutant phenotypes shows that embryos with no maternal contribution of dQ2 die at embryonic stage, and mutant adult flies rest less compared to wild type. These results suggest dQ2 is a novel fly channel that is important in development and plays a role in controlling neuronal excitability.

Notes:

Thesis (Ph.D. in Neuroscience) -- University of Pennsylvania, 2002.

Source: Dissertation Abstracts International, Volume: 63-05, Section: B, page: 2238.

Supervisor: Irwin Levitan.

Local Notes:

School code: 0175.

ISBN:

9780493704173

Access Restriction:

Restricted for use by site license.