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Structural features of LC8-induced self-association of swallow.

ABSTRACT: Cell functions depend on the collective activity of protein networks within which a few proteins, called hubs, participate in a large number of interactions. Dynein light chain LC8, first discovered as a subunit of the motor protein dynein, is considered to have a role broader than that of dynein, and its participation in diverse systems fits the description of a hub. Among its partners is Swallow with which LC8 is essential for proper localization of bicoid mRNA at the anterior cortex of Drosophila oocytes. Why LC8 is essential in this process is not clear, but emerging evidence suggests that LC8 functions by promoting self-association and/or structural organization of its diverse binding partners. This work addresses the energetics and structural features of LC8-induced Swallow self-association distant from LC8 binding. Mutational design based on a hypothetical helical wheel, intermonomer nuclear Overhauser effects assigned to residues expected at interface positions, and circular dichroism spectral characteristics indicate that the LC8-promoted dimer of Swallow is a coiled coil. Secondary chemical shifts and (15)N backbone relaxation identify the boundaries and distinguishing structural features of the coiled coil. Thermodynamic analysis of Swallow polypeptides designed to decouple self-association from LC8 binding reveals that the higher binding affinity of the engineered bivalent Swallow is of purely entropic origin and that the linker separating the coiled coil from the LC8 binding site remains disordered. We speculate that the LC8-promoted coiled coil is critical for bicoid mRNA localization because it favors structural organization of Swallow, which except for the central LC8-promoted coiled coil is primarily disordered.

SUBMITTER: Kidane AI

PROVIDER: S-EPMC3830627 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Structural features of LC8-induced self-association of swallow.

Kidane Ariam I AI Song Yujuan Y Nyarko Afua A Hall Justin J Hare Michael M Löhr Frank F Barbar Elisar E

Biochemistry 20130821 35

Cell functions depend on the collective activity of protein networks within which a few proteins, called hubs, participate in a large number of interactions. Dynein light chain LC8, first discovered as a subunit of the motor protein dynein, is considered to have a role broader than that of dynein, and its participation in diverse systems fits the description of a hub. Among its partners is Swallow with which LC8 is essential for proper localization of bicoid mRNA at the anterior cortex of Drosop ...[more]

PMID: 23914803

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Project description:BackgroundDynein Light Chain 1 (LC8) has been shown to pull down tubulin subunits, suggesting that it interacts with microtubules.ResultsLC8 decorates microtubules in vitro and in Drosophila embryos, promotes microtubule assembly, and stabilizes microtubules both in vitro and in tissue-cultured cells.ConclusionLC8 stabilizes microtubules.SignificanceData provide the first evidence of a novel MAP-like function of LC8. Dynein light chain 1 (LC8), a highly conserved protein, is known to bind to a variety of different polypeptides. It functions as a dimer, which is inactivated through phosphorylation at the Ser-88 residue. A loss of LC8 function causes apoptosis in Drosophila embryos, and its overexpression induces malignant transformation of breast cancer cells. Here we show that LC8 binds to tubulin, promotes microtubule assembly, and induces the bundling of reconstituted microtubules in vitro. Furthermore, LC8 decorates microtubules both in Drosophila embryos and in HeLa cells, increases the microtubule stability, and promotes microtubule bundling in these cells. Microtubule stability influences a number of different cellular functions including mitosis and cell differentiation. The LC8 overexpression reduces the susceptibility of microtubules to cold and nocodazole-induced depolymerization in tissue-cultured cells and increases microtubule acetylation, suggesting that LC8 stabilizes microtubules. We also show that LC8 knockdown or transfection with inhibitory peptides destabilizes microtubules and inhibits bipolar spindle assembly in HeLa cells. In addition, LC8 knockdown leads to the mitotic block in HeLa cells. Furthermore, molecular docking analysis using the crystal structures of tubulin and LC8 dimer indicated that the latter may bind at α-β tubulin junction in a protofilament at sites distinct from the kinesin and dynein binding sites. Together, we provide the first evidence of a novel microtubule-associated protein-like function of LC8 that could explain its reported roles in cellular metastasis and differentiation.

Dataset Information

Structural features of LC8-induced self-association of swallow.

Publications

Structural features of LC8-induced self-association of swallow.

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