Dev Biol. 2005 Oct 1;286(1):326-37.

Junctate, an inositol 1,4,5-triphosphate receptor associated protein, is present in rodent sperm and binds TRPC2 and TRPC5 but not TRPC1 channels.External 2231691f894ba696de1310221b0a0dbbb31a7251e75115c265587c3d9d5f507c

Stamboulian, S., Moutin, M. J., Treves, S., Pochon, N., Grunwald, D., Zorzato, F., De Waard, M., Ronjat, M., Arnoult, C.,
["CEA/Grenoble, Laboratoire Canaux Calciques, Fonctions et Pathologies, Unite mixte INSERM U607, 17 rue des martyrs, F-38054 Grenoble Cedex 9, France."]
The acrosome reaction, the first step of the fertilization, is induced by calcium influx through Canonical Transient Receptor Potential channels (TRPC). The molecular nature of TRPC involved is still a debated question. In mouse, TRPC2 plays the most important role and is responsible for the calcium plateau. However, TRPC1 and TRPC5 are also localized in the acrosomal crescent of the sperm head and may participate in calcium signaling, especially in TRPC2-deficient mice. Activation of TRPC channels is an unresolved question in germ and somatic cells as well. In particular, in sperm, little is known concerning the molecular events leading to TRPC2 activation. From the discovery of IP3R binding domains on TRPC2, it has been suggested that TRPC channel activation may be due to a conformational coupling between IP3R and TRPC channels. Moreover, recent data demonstrate that junctate, an IP3R associated protein, participates also in the gating of some TRPC. In this study, we demonstrate that junctate is expressed in sperm and co-localizes with the IP3R in the acrosomal crescent of the anterior head of rodent sperm. Consistent with its specific localization, we show by pull-down experiments that junctate interacts with TRPC2 and TRPC5 but not with TRPC1. We focused on the interaction between TRPC2 and junctate, and we show that the N-terminus of junctate interacts with the C-terminus of TRPC2, both in vitro and in a heterologous expression system. We show that junctate binds to TRPC2 independently of the calcium concentration and that the junctate binding site does not overlap with the common IP3R/calmodulin binding sites. TRPC2 gating is downstream phospholipase C activation, which is a key and necessary step during the acrosome reaction. TRPC2 may then be activated directly by diacylglycerol (DAG), as in neurons of the vomeronasal organ. In the present study, we investigated whether DAG could promote the acrosome reaction. We found that 100 microM OAG, a permeant DAG analogue, was unable to trigger the acrosome reaction. Altogether, these results provide a new hypothesis concerning sperm TRPC2 gating: TRPC2 activation may be due to modifications of its interaction with both junctate and IP3R, induced by depletion of calcium from the acrosomal vesicle.
PMID: 16153633External 2231691f894ba696de1310221b0a0dbbb31a7251e75115c265587c3d9d5f507c
Screening Toggle 893349bafcc528f8346c51dc3420151d67b0126b2c122dd1017121c03fa0f69b
  Experimental screening Non-experimental screening Reference
TRP channel construct Interactor source
TRP channel Interactor Method Species Region Species Organ/tissue Sample type
TRPC2 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Junctate Inference Prediction 16153633
TRPC5 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Junctate Inference Prediction 16153633
(Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4: click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
Validation: In vitro validation Toggle 893349bafcc528f8346c51dc3420151d67b0126b2c122dd1017121c03fa0f69b
  Assay with recombinant proteins Reference
TRP channel construct Interactor construct
TRP channel Interactor Method Species Region Expression system Species Region Expression system
TRPC2 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Calmodulin Fusion protein-pull down assay Mouse 925-1172 E. coli Not specified Full-length In vitro translation 16153633
TRPC2 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Junctate Fusion protein-pull down assay Mouse 925-1172 E. coli Mouse Full-length HEK293 lysates 16153633
TRPC5 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Junctate Fusion protein-pull down assay Not specified Full-length HEK293 lysates Mouse Full-length In vitro translation 16153633
(Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4: click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
Characterization Toggle 893349bafcc528f8346c51dc3420151d67b0126b2c122dd1017121c03fa0f69b
  Binding region mapping Stoichiometry Affinity (Kd) Reference
TRP channel Interactor
TRP channel Interactor Method Species Region Species Region
TRPC2 Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4 Junctate Fusion protein-pull down assay Mouse 925-1172 Mouse 1-25 (in isoform Junctin) 16153633
(Link 2bd4d11adb659cddf58197a94e201f0a44c55d8d7cb427c624971b42e122c0a4: click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
TRP / Interactor

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