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Structural and functional analyses were used to investigate the regulation of the inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) by Ca2+. To define the structural determinants for Ca2+ binding, cDNAs encoding GST fusion proteins that covered the complete linear cytosolic sequence of the InsP3R-1 were expressed in bacteria. The fusion proteins were(More)
Striated muscle represents one of the best models for studies on Ca(2+) signalling. However, although much is known on the localisation and molecular interactions of the ryanodine receptors (RyRs), far less is known on the localisation and on the molecular interactions of the inositol trisphosphate receptors (InsP(3)Rs) in striated muscle cells. Recently,(More)
Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) induces Ca2+ oscillations and waves in Xenopus laevis oocytes. Microsomes from oocytes exhibit high-affinity binding for Ins(1,4,5)P3, and demonstrate Ins(1,4,5)P3-induced Ca2+ release. The Ins(1,4,5)P3 receptor (InsP3R) was purified from oocyte microsomes as a large tetrameric complex and shown to have a monomer(More)
During maturation, mammalian oocytes undergo a series of changes that prepare them for fertilization. These events are regulated by kinases, most notably histone H1 and mitogen-activated protein kinase. Intracellular calcium ([Ca2+]i) oscillations participate in oocyte signaling, and it has been postulated that they play a role in oocyte maturation. In(More)
Elementary Ca(2+) signals, such as "Ca(2+) puffs", which arise from the activation of inositol 1,4,5-trisphosphate receptors, are building blocks for local and global Ca(2+) signalling. We characterized Ca(2+) puffs in six cell types that expressed differing ratios of the three inositol 1,4,5-trisphosphate receptor isoforms. The amplitudes, spatial spreads(More)
Calreticulin is a Ca2+-binding chaperone in the endoplasmic reticulum (ER), and calreticulin gene knockout is embryonic lethal. Here, we used calreticulin-deficient mouse embryonic fibroblasts to examine the function of calreticulin as a regulator of Ca2+ homeostasis. In cells without calreticulin, the ER has a lower capacity for Ca2+ storage, although the(More)
Activation of cells by hormones, growth factors or neurotransmitters leads to an increased production of inositol trisphosphate (InsP3) and, after activation of the InsP3 receptor (InsP3R), to Ca2+ release from intracellular Ca2+ stores. The release of intracellular Ca2+ is characterised by a graded response when submaximal doses of agonists are used. The(More)
The Ca2+ content of the intracellular Ca2+ stores controls the inositol 1,4,5-trisphosphate receptor (InsP3R) in the clonal cell line A7r5. This regulation was characterized with respect to the understanding of the "quantal" release phenomenon. Independent of the loading protocol used, increasing the Ca2+ content of the stores increased the sensitivity of(More)
In mammalian fertilization, inositol 1,4,5-trisphosphate receptor (IP3R)-dependent Ca2+ release is a crucial signaling event that originates from the vicinity of sperm-egg interaction and spreads as a wave throughout the egg cytoplasm. While it is known that Ca2+ is released by the type 1 IP3R in the egg cortex, the potential involvement of other isoform(More)
In almost all cells, cytosolic Ca(2+) is a crucial intracellular messenger, regulating many cellular processes. In non-excitable as well as in some excitable cells, Ca(2+) release from the intracellular stores into the cytoplasm is primarily initiated by the second messenger inositol 1,4,5-trisphosphate (IP(3)), which interacts with the IP(3) receptor(More)