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Alternative splicing, muscle calcium sensitivity, and the modulation of dragonfly flight performance.

ABSTRACT: Calcium sensitivity of myosin cross-bridge activation in striated muscles commonly varies during ontogeny and in response to alterations in muscle usage, but the consequences for whole-organism physiology are not well known. Here we show that the relative abundances of alternatively spliced transcripts of the calcium regulatory protein troponin T (TnT) vary widely in flight muscle of Libellula pulchella dragonflies, and that the mixture of TnT splice variants explains significant portions of the variation in muscle calcium sensitivity, wing-beat frequency, and an index of aerodynamic power output during free flight. Two size-distinguishable morphs differ in their maturational pattern of TnT splicing, yet they show the same relationship between TnT transcript mixture and calcium sensitivity and between calcium sensitivity and aerodynamic power output. This consistency of effect in different developmental and physiological contexts strengthens the hypothesis that TnT isoform variation modulates muscle calcium sensitivity and whole-organism locomotor performance. Modulating muscle power output appears to provide the ecologically important ability to operate at different points along a tradeoff between performance and energetic cost.

SUBMITTER: Marden JH

PROVIDER: S-EPMC24815 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Alternative splicing, muscle calcium sensitivity, and the modulation of dragonfly flight performance.

Marden J H JH Fitzhugh G H GH Wolf M R MR Arnold K D KD Rowan B B

Proceedings of the National Academy of Sciences of the United States of America 19991201 26

Calcium sensitivity of myosin cross-bridge activation in striated muscles commonly varies during ontogeny and in response to alterations in muscle usage, but the consequences for whole-organism physiology are not well known. Here we show that the relative abundances of alternatively spliced transcripts of the calcium regulatory protein troponin T (TnT) vary widely in flight muscle of Libellula pulchella dragonflies, and that the mixture of TnT splice variants explains significant portions of the ...[more]

PMID: 10611380

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Project description:Calcium ion channels coordinate an astounding number of cellular functions. Surprisingly, only 10 Ca(V)alpha(1) subunit genes encode the structural cores of all voltage-gated calcium channels. What mechanisms exist to modify the structure of calcium channels and optimize their coupling to the rich spectrum of cellular functions? Growing evidence points to the contribution of post-translational alternative processing of calcium channel RNA as the main mechanism for expanding the functional potential of this important gene family. Alternative splicing of RNA is essential during neuronal development where fine adjustments in protein signaling promote and inhibit cell-cell interactions and underlie axonal guidance. However, attributing a specific functional role to an individual splice isoform or splice site has been difficult. In this regard, studies of ion channels are advantageous because their function can be monitored with precision, allowing even subtle changes in channel activity to be detected. Such studies are especially insightful when coupled with information about isoform expression patterns and cellular localization. In this paper, we focus on two sites of alternative splicing in the N-type calcium channel Ca(V)2.2 gene. We first describe cassette exon 18a that encodes a 21 amino acid segment in the II-III intracellular loop region of Ca(V)2.2. Here, we show that e18a is upregulated in the nervous system during development. We discuss these new data in light of our previous reports showing that e18a protects the N-type channel from cumulative inactivation. Second, we discuss our published data on exons e37a and e37b, which encode 32 amino acids in the intracellular C-terminus of Ca(V)2.2. These exons are expressed in a mutually exclusive manner. Exon e37a-containing Ca(V)2.2 mRNAs and their resultant channels express at higher density in dorsal root ganglia and, as we showed recently, e37a increases N-type channel sensitivity to G-protein-mediated inhibition, as compared to generic e37b-containing N-type channels.

Dataset Information

Alternative splicing, muscle calcium sensitivity, and the modulation of dragonfly flight performance.

Publications

Alternative splicing, muscle calcium sensitivity, and the modulation of dragonfly flight performance.

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