Contribution of Ryanodine Receptor Subtype 3 to Ca2+Responses in Ca2+-overloaded Cultured Rat Portal Vein Myocytes

Ryanodine receptors (RyRs) are intracellular calcium release channels that are highly expressed in striated muscle and neurons but are also detected in several non-excitable cells. We have studied the expression of the three RyR isoforms in male germ cells at different stages of maturation by western blot and RT-PCR. RyR1 was expressed in spermatogonia, pachytene spermatocytes and round spermatids whereas RyR2 was found only in 5- to 10-day-old testis but not in germ cells. RyR3 was not revealed at the protein level, although its mRNA was detected in mixed populations of germ cells. Caffeine, a known agonist of RyRs, was able to induce release of Ca 2+ from intracellular stores in spermatogonia, pachytene spermatocytes and round spermatids, but not spermatozoa. Treatment with high doses of ryanodine, which are known to block RyR channel activity, reduced spermatogonial proliferation and induced meiosis in in vitro organ cultures of testis from 7-day-old mice. In conclusion, the results presented here indicate that RyRs are present in germ cells and that calcium mobilization through RyR channels could participate to the regulation of male germ maturation

Section: Discussioncontrasting

confidence: 40%

Ryanodine receptors are expressed and functionally active in mouse spermatogenic cells and their inhibition interferes with spermatogonial differentiation

Chiarella

Puglisi

Sorrentino

et al. 2004

“…In arterial Journal of Cell Science 117 (13) vascular smooth muscle cells, a contribution by RyR3, in addition to RyR1 and RyR2, to Ca 2+ spark generation has been suggested based on results from RyR3-deficient mice (Lohn et al, 2001). A similar contribution of RyR3 to cellular Ca 2+ signalling has been suggested in Ca 2+ -overloaded cultured rat portal vein smooth muscle cells (Mironneau et al, 2001). It has been found, however, that the RyR3 splice variant predominantly expressed in smooth muscle is not a functional Ca 2+ release channel, but it could function in a dominant negative fashion (Jiang et al, 2003).…”

Section: Discussionmentioning

confidence: 63%

Requirement of ryanodine receptors for pacemaker Ca2+ activity in ICC and HEK293 cells

Aoyama

Yamada

Wang

et al. 2004

Intracellular Ca2+ ([Ca2+]i) oscillations seen in interstitial cells of Cajal (ICCs) are considered to be the primary pacemaker activity in the gut. Here, we show evidence that periodic Ca2+ release from intracellular Ca2+ stores produces [Ca2+]i oscillations in ICCs, using cell cluster preparations isolated from mouse ileum. The pacemaker [Ca2+]i oscillations in ICCs are preserved in the presence of dihydropyridine Ca2+ antagonists, which suppress Ca2+ activity in smooth muscle cells. However, applications of drugs affecting either ryanodine receptors or inositol 1,4,5-trisphosphate receptors terminated [Ca2+]i oscillations at relatively low concentrations. RT-PCR analyses revealed a predominant expression of type 3 RyR (RyR3) in isolated c-Kit-immunopositive cells (ICCs). Furthermore, we demonstrate that pacemaker-like global [Ca2+]i oscillation activity is endowed by introducing RyR3 into HEK293 cells, which originally express only IP3Rs. The reconstituted [Ca2+]i oscillations in HEK293 cells possess essentially the same pharmacological characteristics as seen in ICCs. The results support the functional role of RyR3 in ICCs.

“…However, under conditions of Ca 2+ overload (superfusion with 10 mM Ca 2+ ), previous microinjection with antisense oligonucleotides directed against type 3 RyR reduced the global Ca 2+ responses induced by phenylephrine and caffeine, but not spontaneous Ca 2+ sparks (Mironneau et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Amplification and propagation of pacemaker Ca2+ signals by cyclic ADP-ribose and the type 3 ryanodine receptor in T cells

Kunerth

Langhorst

Schwarzmann

et al. 2004

Ligation of the T-cell receptor/CD3 complex results in global Ca2+ signals that are essential for T-cell activation. We have recently reported that these global Ca2+ signals are preceded by localized pacemaker Ca2+ signals. Here, we demonstrate for the first time for human T cells that an increase in signal frequency of subcellular pacemaker Ca2+ signals at sites close to the plasma membrane, in the cytosol and in the nucleus depends on the type 3 ryanodine receptor (RyR) and its modulation by cyclic ADP-ribose. The spatial distribution of D-myo-inositol 1,4,5-trisphosphate receptors and RyRs indicates a concerted action of both of these receptors/Ca2+ channels in the generation of initial pacemaker signals localized close to the plasma membrane. Inhibition or knockdown of RyRs resulted in significant decreases in (1) the frequency of initial pacemaker signals localized close to the plasma membrane, and (2) the frequency of localized pacemaker Ca2+ signals in the inner cytosol. Moreover, upon microinjection of cyclic ADP-ribose or upon extracellular addition of its novel membrane-permeant mimic N-1-ethoxymethyl-substituted cyclic inosine diphosphoribose, similarly decreased Ca2+ signals were observed in both type 3 RyR-knockdown cells and in control cells microinjected with the RyR antagonist Ruthenium Red. Taken together, our results show that, under physiological conditions in human T cells, RyRs play crucial roles in the local amplification and the spatiotemporal development of subcellular Ca2+ pacemaker signals.