Sammels Eva, Devogelaere Benoit, Mekahli Djalila, Bultynck Geert, Missiaen Ludwig, Parys Jan B, De Smedt Humbert
Laboratory of Molecular and Cellular Signaling; Department of Molecular Cell Biology; K.U. Leuven, Leuven Belgium.
Commun Integr Biol. 2010 Nov;3(6):530-2. doi: 10.4161/cib.3.6.12751. Epub 2010 Nov 1.
Autosomal dominant polycystic kidney disease (ADPKD) arises as a consequence of mutations of the genes PKD1 and PKD2, encoding respectively the integral membrane proteins polycystin-1 and polycystin-2 (TRPP2), resulting in a disturbance in intracellular Ca(2+) signaling. Previously we investigated the interaction between TRPP2 and the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R), an intracellular Ca(2+) channel in the endoplasmic reticulum (ER). We identified the molecular determinants of this interaction and observed an enhanced IP(3)-induced Ca(2+) release (IICR). Since we found that TRPP2 strongly bound to a cluster of positively charged amino acids in the N-terminal ligand-binding domain (LBD) of the IP(3)R, we now investigated whether TRPP2 would interfere with the binding of IP(3) to the IP(3)R. In in vitro experiments we observed that TRPP2 partially inhibited the binding of IP(3) to the LBD of the IP(3)R with an IC(50) of ∼350 nM. The suppressor domain, i.e., the N-terminal 225 amino acids of the LBD of the IP(3)R, mediated this inhibitory effect of TRPP2 on IP(3) binding. The observation that the interaction between the IP(3)R and TRPP2 decreased IP(3) binding is in apparent contrast to the increased IICR. The data can be explained however by a subsequent activation of Ca(2+)-induced Ca(2+) release (CICR) via TRPP2. Implications of this mechanism for cellular Ca(2+) signaling are discussed in this addendum.
常染色体显性遗传性多囊肾病（ADPKD）是由PKD1和PKD2基因突变引起的，这两个基因分别编码整合膜蛋白多囊蛋白-1和多囊蛋白-2（TRPP2），导致细胞内Ca(2+)信号传导紊乱。此前我们研究了TRPP2与内质网（ER）中的细胞内Ca(2+)通道——肌醇1,4,5-三磷酸（IP(3)）受体（IP(3)R）之间的相互作用。我们确定了这种相互作用的分子决定因素，并观察到IP(3)诱导的Ca(2+)释放（IICR）增强。由于我们发现TRPP2与IP(3)R的N端配体结合结构域（LBD）中的一组带正电荷的氨基酸簇紧密结合，我们现在研究TRPP2是否会干扰IP(3)与IP(3)R的结合。在体外实验中，我们观察到TRPP2以约350 nM的IC(50)部分抑制IP(3)与IP(3)R的LBD的结合。抑制结构域，即IP(3)R的LBD的N端225个氨基酸，介导了TRPP2对IP(3)结合的这种抑制作用。IP(3)R与TRPP2之间的相互作用降低了IP(3)结合这一观察结果与IICR增加明显相反。然而，这些数据可以通过随后经由TRPP2的Ca(2+)诱导的Ca(2+)释放（CICR）激活来解释。本附录讨论了这种机制对细胞Ca(2+)信号传导的影响。
