Molecular Evolution and Functional Divergence of the Ca2+ Sensor Protein in Store-operated Ca2+ Entry: Stromal Interaction Molecule

Receptor-mediated Ca2+ signaling in many non-excitable cells initially induces Ca2+ release from intracellular Ca2+ stores, followed by Ca2+ influx across the plasma membrane. Recent findings have suggested that stromal interaction molecules (STIMs) function as the Ca2+ sensor to detect changes of Ca2+ content in the intracellular Ca2+ stores. Human STIMs and invertebrate STIM share several functionally important protein domains, but diverge significantly in the C-terminus. To better understand the evolutionary significance of STIM activity, phylogenetic analysis of the STIM protein family was conducted after extensive database searching. Results from phylogeny and sequence analysis revealed early adaptation of the C-terminal divergent domains in Urochordata, before the expansion of STIMs in Vertebrata. STIMs were subsequently subjected to one round of gene duplication as early as in the Euteleostomi lineage in vertebrates, with a second round of fish-specific gene duplication. After duplication, STIM-1 and STIM-2 molecules appeared to have undergone purifying selection indicating strong evolutionary constraints within each group. Furthermore, sequence analysis of the EF-hand Ca2+ binding domain and the SAM domain, together with functional divergence studies, identified critical regions/residues likely underlying functional changes, and provided evidence for the hypothesis that STIM-1 and STIM-2 might have developed distinct functional properties after duplication

Development and Application Based on MTS Hybrid Test System

It is meaningful to further explore the hardware and software functions of MTS loading system widely used in building structure test at home and abroad. This paper proposes a kind of seismic pseudo-dynamic test method based on internal command control of software. Three programs including monitor station, sincycle test and rampcontrol test were developed by VB, and the connection with NetSLab platform was completed via master-slaver network, then the test system was established. A single degree of freedom hybrid test of single span bridge was carried out, and a short column of CFRP reinforced was used to be an experimental element. Secondary load for the partial damaged model was implemented to research the mechanics performance of the specimen. The result confirms that the established system is capable of conducting the pseudo-dynamic hybrid test. The hybrid test demonstrates that the proposed internal command control method is feasible and effective, which can provide reference for the system development and seismic research

A plastid two-pore channel essential for inter-organelle communication and growth of Toxoplasma gondii.

Two-pore channels (TPCs) are a ubiquitous family of cation channels that localize to acidic organelles in animals and plants to regulate numerous Ca2+-dependent events. Little is known about TPCs in unicellular organisms despite their ancient origins. Here, we characterize a TPC from Toxoplasma gondii, the causative agent of toxoplasmosis. TgTPC is a member of a novel clad of TPCs in Apicomplexa, distinct from previously identified TPCs and only present in coccidians. We show that TgTPC localizes not to acidic organelles but to the apicoplast, a non-photosynthetic plastid found in most apicomplexan parasites. Conditional silencing of TgTPC resulted in progressive loss of apicoplast integrity, severely affecting growth and the lytic cycle. Isolation of TPC null mutants revealed a selective role for TPCs in replication independent of apicoplast loss that required conserved residues within the pore-lining region. Using a genetically-encoded Ca2+ indicator targeted to the apicoplast, we show that Ca2+ signals deriving from the ER but not from the extracellular space are selectively transmitted to the lumen. Deletion of the TgTPC gene caused reduced apicoplast Ca2+ uptake and membrane contact site formation between the apicoplast and the ER. Fundamental roles for TPCs in maintaining organelle integrity, inter-organelle communication and growth emerge

CatSperζ regulates the structural continuity of sperm Ca2+ signaling domains and is required for normal fertility

We report that the Gm7068 (CatSpere) and Tex40 (CatSperz) genes encode novel subunits of a 9-subunit CatSper ion channel complex. Targeted disruption of CatSperz reduces CatSper current and sperm rheotactic efficiency in mice, resulting in severe male subfertility. Normally distributed in linear quadrilateral nanodomains along the flagellum, the complex lacking CatSperζ is disrupted at ~0.8 μm intervals along the flagellum. This disruption renders the proximal flagellum inflexible and alters the 3D flagellar envelope, thus preventing sperm from reorienting against fluid flow in vitro and efficiently migrating in vivo. Ejaculated CatSperz-null sperm cells retrieved from the mated female uterus partially rescue in vitro fertilization (IVF) that failed with epididymal spermatozoa alone. Human CatSperε is quadrilaterally arranged along the flagella, similar to the CatSper complex in mouse sperm. We speculate that the newly identified CatSperζ subunit is a late evolutionary adaptation to maximize fertilization inside the mammalian female reproductive tract. DOI: http://dx.doi.org/10.7554/eLife.23082.00

Evolutionary Genomics Reveals Lineage-Specific Gene Loss and Rapid Evolution of a Sperm-Specific Ion Channel Complex: CatSpers and CatSperβ

The mammalian CatSper ion channel family consists of four sperm-specific voltage-gated Ca2+ channels that are crucial for sperm hyperactivation and male fertility. All four CatSper subunits are believed to assemble into a heteromultimeric channel complex, together with an auxiliary subunit, CatSperβ. Here, we report a comprehensive comparative genomics study and evolutionary analysis of CatSpers and CatSperβ, with important correlation to physiological significance of molecular evolution of the CatSper channel complex. The development of the CatSper channel complex with four CatSpers and CatSperβ originated as early as primitive metazoans such as the Cnidarian Nematostella vectensis. Comparative genomics revealed extensive lineage-specific gene loss of all four CatSpers and CatSperβ through metazoan evolution, especially in vertebrates. The CatSper channel complex underwent rapid evolution and functional divergence, while distinct evolutionary constraints appear to have acted on different domains and specific sites of the four CatSper genes. These results reveal unique evolutionary characteristics of sperm-specific Ca2+ channels and their adaptation to sperm biology through metazoan evolution