Glucose-induced calcium influx in budding yeast involves a novel calcium transport system and can activate calcineurin

FigA, a Putative Homolog of Low-Affinity Calcium System Member Fig1 in Saccharomyces cerevisiae, Is Involved in Growth and Asexual and Sexual Development in Aspergillus nidulans

“…Therefore, the name FIG1 (mating factor-induced gene 1) was initially used to describe this gene. Moreover, previous studies have verified that orthologs of FIG1 also exist in the genomes of the fission yeast and filamentous fungi (5,18,19). As a member of the PMP22/claudin superfamily, Fig1 shares several common structural characteristics with its mammalian orthologs, such as the presence of four putative transmembrane domains and a conserved claudin motif [GGXC(n)C, where is a hydrophobic amino acid and n is any number of amino acids] in the first large extracellular loop (3,19).…”

“…The HACS is responsible primarily for the pheromone-induced calcium response in minimal medium, but in rich medium, the function of the HACS is strongly inhibited by calcineurin so that the LACS becomes essential for this response. The HACS consists of at least two known subunits, the voltagegated calcium channel (VGCC) homolog Cch1 and the stretchactivated calcium channel/regulatory protein Mid1, which usually form a complex to become the major calcium entry route under low-calcium conditions (5,(7)(8)(9)(10)(11). To date, the predicted homologs of Cch1 and Mid1 have been intensively studied in many types of fungi.…”

“…In yeasts, at least two different calcium uptake systems, the highaffinity calcium influx system (HACS) and the low-affinity calcium influx system (LACS), have been identified during the mating process (3)(4)(5)(6). The HACS is responsible primarily for the pheromone-induced calcium response in minimal medium, but in rich medium, the function of the HACS is strongly inhibited by calcineurin so that the LACS becomes essential for this response.…”

Role of Fig1, a Component of the Low-Affinity Calcium Uptake System, in Growth and Sexual Development of Filamentous Fungi

“…In fungi, two major calcium uptake pathways have been identified and characterized: the high-affinity calcium uptake system (HACS), active during low calcium availability, and the low-affinity calcium uptake system (LACS), active when calcium availability is high (24,27,38,45,50). A third calcium uptake pathway was recently described for Saccharomyces cerevisiae but has yet to have its genetic components identified (34). In the filamentous fungus Fusarium graminearum (sexual-stage Gibberella zeae), the causal agent of head blight of wheat and barley, calcium signaling has been shown to have a role in hyphal growth, sporulation, and fruiting body function, and the regulation of components of the HACS has been shown to be involved in these processes (17,35,62,63).…”

The Lectin Chaperone Calnexin Is Involved in the Endoplasmic Reticulum Stress Response by Regulating Ca 2+ Homeostasis in Aspergillus nidulans

“…Subsequently, an increased cytosolic free calcium concentration ([Ca 2ϩ ] c ) returns to its normally low resting level within the cytosol due to various calcium pumps and calcium antiporters, as well as cytoplasmic calcium buffering (8,9). Two different calcium carrier systems have been identified in most fungal species: the high-affinity Ca 2ϩ influx system (HACS) and the low-affinity calcium influx system (LACS) (10)(11)(12)(13). The main components of the HACS are an ␣ subunit of the mammalian voltage-gated Ca 2ϩ -channel homolog Cch1 and a stretch-activated ␤ subunit called Mid1 (14)(15)(16).…”