Expression of inositol 1,4,5-trisphosphate receptors changes the Ca2+ signal of Xenopus oocytes

1996 ◽  
Vol 270 (4) ◽  
pp. C1255-C1261 ◽  
Author(s):  
S. DeLisle ◽  
O. Blondel ◽  
F. J. Longo ◽  
W. E. Schnabel ◽  
G. I. Bell ◽  
...  

The receptors for the second messenger inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] form a family of closely related proteins that play an important role in regulating the free intracellular Ca2+ concentration. To test the hypothesis that changing the expression level of Ins(1,4,5)P3 receptors could alter the Ins(1,4,5)P3-mediated Ca2+ signal, we overexpressed Ins(1,4,5)P3 receptor type 1 (InsP3R-1) or type 3 (InsP3R-3) in Xenopus laevis oocytes. Expression of InsP3R-1 increased the velocity of the propagating waves of intracellular Ca2+ release but did not affect the Ins(1,4,5)P3-induced entry of extracellular Ca2+ across the plasma membrane. In contrast, expression of intracellular Ca2+ but markedly increased the magnitude and duration of Ca2+ influx. Immunolocalization studied revealed InsP3R-3 at the endoplasmic reticulum, with a relatively stronger signal at or near the plasma membrane. The results suggest that changing the expression level of an InsP3R can alter the Ins(1,4,5)P3-mediated Ca2+ signal and that InsP3R-1 and InsP3R-3 may have different biological functions.

Cell Calcium ◽  
2000 ◽  
Vol 27 (5) ◽  
pp. 257-267 ◽  
Author(s):  
K. Maes ◽  
L. Missiaen ◽  
P. De Smet ◽  
S. Vanlingen ◽  
G. Callewaert ◽  
...  

2004 ◽  
Vol 287 (4) ◽  
pp. C1114-C1124 ◽  
Author(s):  
Nelson P. Barrera ◽  
Bernardo Morales ◽  
Manuel Villalón

An increase in intracellular free Ca2+ concentration ([Ca2+]i) has been shown to be involved in the increase in ciliary beat frequency (CBF) in response to ATP; however, the signaling pathways associated with inositol 1,4,5-trisphosphate (IP3) receptor-dependent Ca2+ mobilization remain unresolved. Using radioimmunoassay techniques, we have demonstrated the appearance of two IP3 peaks occurring 10 and 60 s after ATP addition, which was strongly correlated with a release of intracellular Ca2+ from internal stores and an influx of extracellular Ca2+, respectively. In addition, ATP-dependent Ca2+ mobilization required protein kinase C (PKC) and Ca2+/calmodulin-dependent protein kinase II activation. We found an increase in PKC activity in response to ATP, with a peak at 60 s after ATP addition. Xestospongin C, an IP3 receptor blocker, significantly diminished both the ATP-induced increase in CBF and the initial transient [Ca2+]i component. ATP addition in the presence of xestospongin C or thapsigargin revealed that the Ca2+ influx is also dependent on IP3 receptor activation. Immunofluorescence and confocal microscopic studies showed the presence of IP3 receptor types 1 and 3 in cultured ciliated cells. Immunogold electron microscopy localized IP3 receptor type 3 to the nucleus, the endoplasmic reticulum, and, interestingly, the plasma membrane. In contrast, IP3 receptor type 1 was found exclusively in the nucleus and the endoplasmic reticulum. Our study demonstrates for the first time the presence of IP3 receptor type 3 in the plasma membrane in ciliated cells and leads us to postulate that the IP3 receptor can directly trigger Ca2+ influx in response to ATP.


1996 ◽  
Vol 109 (6) ◽  
pp. 1285-1295
Author(s):  
F. Le Caherec ◽  
P. Bron ◽  
J.M. Verbavatz ◽  
A. Garret ◽  
G. Morel ◽  
...  

Xenopus laevis oocytes are widely used as an expression system for plasma membrane proteins, achieved by cytoplasmic microinjection of messenger RNA. In the present study, we propose an alternative system allowing functional insertion of exogenous proteins into the plasma membrane of Xenopus oocytes. We microinjected proteoliposome suspensions into the cytoplasm and then analyzed membrane protein function. The proteins used in this work were members of the MIP family: the human erythrocyte water channel aquaporin 1 (AQP1), the major intrinsic protein (MIP26) from bovine eye lens and a 25 kDa polypeptide (P25) from a water shunting complex found in the digestive tract of an homopteran sap-sucking insect (Cicadella viridis). Proteoliposomes containing either AQP1, MIP26, or P25 were injected into Xenopus oocytes. The subsequent insertion of these proteins into the plasma membrane of oocytes was demonstrated by immunocytochemistry. Oocytes microinjected with either AQP1 or P25-proteoliposomes exhibited significantly increased osmotic membrane water permeabilities (Pf = 3.16 +/- 026 and 4.03 +/- 0.26 × 10(−3) cm/second, respectively) compared to those measured for oocytes injected with liposomes alone or with MIP26-proteoliposomes (Pf = 1.39 +/- 0.07 and 1.44 +/- 0.10 × 10(−3) cm/second, respectively). These effects were inhibited by HgCl2 in a reversible manner. Arrhenius activation energies of water transfer were low when AQP1 or P25 were present in oocyte plasma membranes (Ea = 2.29 and 3.01 kcal/mol, respectively, versus Ea = 11.75 kcal/mol for liposome injected oocytes). The properties observed here for AQP1 are identical to those widely reported following AQP1 cRNA expression in oocytes. From the present study, we conclude that: (1) exogenous plasma membrane proteins incorporated into liposomes and microinjected into the cytoplasm of Xenopus oocytes are subsequently found in the plasma membrane of the oocytes in a functional state; and (2) in this system, the P25 polypeptide from the MIP family found in the digestive tract of Cicadella viridis exhibits properties similar to those described for the archetype of water channels AQP1, and thus is a new member of the aquaporin family.


2001 ◽  
Vol 117 (5) ◽  
pp. 435-446 ◽  
Author(s):  
Don-On Daniel Mak ◽  
Sean McBride ◽  
J. Kevin Foskett

The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) is an endoplasmic reticulum–localized Ca2+-release channel that controls complex cytoplasmic Ca2+ signaling in many cell types. At least three InsP3Rs encoded by different genes have been identified in mammalian cells, with different primary sequences, subcellular locations, variable ratios of expression, and heteromultimer formation. To examine regulation of channel gating of the type 3 isoform, recombinant rat type 3 InsP3R (r-InsP3R-3) was expressed in Xenopus oocytes, and single-channel recordings were obtained by patch-clamp electrophysiology of the outer nuclear membrane. Gating of the r-InsP3R-3 exhibited a biphasic dependence on cytoplasmic free Ca2+ concentration ([Ca2+]i). In the presence of 0.5 mM cytoplasmic free ATP, r-InsP3R-3 gating was inhibited by high [Ca2+]i with features similar to those of the endogenous Xenopus type 1 InsP3R (X-InsP3R-1). Ca2+ inhibition of channel gating had an inhibitory Hill coefficient of ∼3 and half-maximal inhibiting [Ca2+]i (Kinh) = 39 μM under saturating (10 μM) cytoplasmic InsP3 concentrations ([InsP3]). At [InsP3] < 100 nM, the r-InsP3R-3 became more sensitive to Ca2+ inhibition, with the InsP3 concentration dependence of Kinh described by a half-maximal [InsP3] of 55 nM and a Hill coefficient of ∼4. InsP3 activated the type 3 channel by tuning the efficacy of Ca2+ to inhibit it, by a mechanism similar to that observed for the type 1 isoform. In contrast, the r-InsP3R-3 channel was uniquely distinguished from the X-InsP3R-1 channel by its enhanced Ca2+ sensitivity of activation (half-maximal activating [Ca2+]i of 77 nM instead of 190 nM) and lack of cooperativity between Ca2+ activation sites (activating Hill coefficient of 1 instead of 2). These differences endow the InsP3R-3 with high gain InsP3–induced Ca2+ release and low gain Ca2+–induced Ca2+ release properties complementary to those of InsP3R-1. Thus, distinct Ca2+ signals may be conferred by complementary Ca2+ activation properties of different InsP3R isoforms.


2009 ◽  
Vol 96 (3) ◽  
pp. 560a
Author(s):  
Matthew J. Betzenhauser ◽  
Larry E. Wagner ◽  
Hyung Seo Park ◽  
Lyndee Knowlton ◽  
David I. Yule

1992 ◽  
Vol 262 (6) ◽  
pp. C1520-C1530 ◽  
Author(s):  
D. Pralong-Zamofing ◽  
Q. H. Yi ◽  
G. Schmalzing ◽  
P. Good ◽  
K. Geering

During progesterone-induced maturation of Xenopus oocytes, the transport and ouabain binding capacity of Na(+)-K(+)-ATPase at the plasma membrane is completely downregulated. To elucidate the mechanism and the physiological significance of this process, we have followed the fate of oocyte alpha-beta 3-Na(+)-K(+)-ATPase complexes during meiotic maturation and early embryonic development. An immunocytochemical follow-up of the catalytic alpha-subunit, ouabain binding studies, cell surface iodination, and oocyte cell fractionation combined with immunochemical subunit detection provides evidence that following progesterone treatment Na(+)-K(+)-ATPase molecules are retrieved from the oocyte plasma membrane. The enzyme complexes are recovered in an active form in an intracellular compartment in both in vitro and in vivo matured eggs. Exogenous Xenopus alpha 1- and beta 1-complexes expressed in the oocyte from injected cRNAs are regulated by progesterone similar to endogenous Na(+)-K(+)-ATPase complexes. Finally, active Na(+)-K+ pumps internalized during oocyte maturation appear to be redistributed to plasma membrane fractions during blastula formation in Xenopus embryos. In conclusion, our data suggest that endocytosis of alpha 1- and beta 3-complexes during meiotic maturation of Xenopus oocytes is responsible for downregulation of Na(+)-K(+)-ATPase activity and results in an intracellular pool of functional enzymes, which might be reexpressed during early development in response to physiological needs.


1994 ◽  
Vol 267 (6) ◽  
pp. C1717-C1722 ◽  
Author(s):  
K. Rezai ◽  
A. Kulisz ◽  
W. J. Wasserman

Progesterone-stimulated Xenopus laevis oocytes undergo an increase in their intracellular pH from 7.3 to 7.7 because of the activation of Na+/H+ antiporters in their plasma membrane. Activation of Na+/H+ exchangers (NHE) in other cell systems appears to be regulated by phosphorylation of the NHE protein. In the current study we demonstrated that cytoplasm taken from steroid-stimulated oocytes rapidly induced an increase in intracellular pH when microinjected into full-grown stage VI recipient oocytes. The protein within the cytoplasm that appears to be responsible for this activity is c-mos kinase. Microinjected pure mosxe kinase protein rapidly activated the Na+/H+ exchangers in full-grown recipient oocytes. Furthermore, injected mosxe protein rapidly activated the Na+/H+ exchangers in smaller progesterone-insensitive stage IV oocytes. Therefore, it appears that the protooncogene product, p39 c-mos kinase, which is normally synthesized in full-grown stage VI oocytes in response to progesterone stimulation, is involved in the upregulation of the Na+/H+ antiporters during oocyte meiotic maturation.


Insects ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 71 ◽  
Author(s):  
Megha Kalsi ◽  
Christopher Gillen ◽  
Peter Piermarini

The yellow fever mosquito Aedes aegypti possesses three genes encoding putative Na+-coupled cation chloride cotransporters (CCCs): aeNKCC1, aeCCC2, and aeCCC3. To date, none of the aeCCCs have been functionally characterized. Here we expressed aeCCC2 heterologously in Xenopus oocytes and measured the uptake of Li+ (a tracer for Na+) and Rb+ (a tracer for K+). Compared to control (H2O-injected) oocytes, the aeCCC2-expressing oocytes exhibited significantly greater uptake of Li+, but not Rb+. However, the uptake of Li+ was neither Cl−-dependent nor inhibited by thiazide, loop diuretics, or amiloride, suggesting unconventional CCC activity. To determine if the Li+-uptake was mediated by a conductive pathway, we performed two-electrode voltage clamping (TEVC) on the oocytes. The aeCCC2 oocytes were characterized by an enhanced conductance for Li+ and Na+, but not K+, compared to control oocytes. It remains to be determined whether aeCCC2 directly mediates the Na+/Li+ conductance or whether heterologous expression of aeCCC2 stimulates an endogenous cation channel in the oocyte plasma membrane.


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