Autosomal dominant polycystic kidney disease is characterized by the loss-of-function of a signaling complex involving polycystin-1 and polycystin-2 (TRPP2, an ion channel of the TRP superfamily), resulting in a disturbance in intracellular Ca 2؉ signaling. Here, we identified the molecular determinants of the interaction between TRPP2 and the inositol 1,4,5-trisphosphate receptor (IP 3 R), an intracellular Ca 2؉ channel in the endoplasmic reticulum. Glutathione S-transferase pulldown experiments combined with mutational analysis led to the identification of an acidic cluster in the C-terminal cytoplasmic tail of TRPP2 and a cluster of positively charged residues in the N-terminal ligand-binding domain of the IP 3 R as directly responsible for the interaction. To investigate the functional relevance of TRPP2 in the endoplasmic reticulum, we re-introduced the protein in TRPP2 ؊/؊ mouse renal epithelial cells using an adenoviral expression system. signaling associated with pathological TRPP2 mutations and therefore contribute to the development of autosomal dominant polycystic kidney disease. Autosomal dominant polycystic kidney disease (ADPKD)4 is an inherited human disorder that affects more than six million people worldwide and is the most common monogenic cause of kidney failure in humans (1). ADPKD results in end-stage renal disease in ϳ50% of the affected individuals by the age of 60. ADPKD arises as a consequence of mutations of two genes PKD1 and PKD2, encoding integral membrane proteins polycystin-1 (PKD1, ϳ460 kDa) and polycystin-2 (TRPP2, ϳ110 kDa), respectively. Most mutations identified in affected families appear to truncate and (or) inactivate either of both proteins (2-5). Mutations in PKD1 account for the vast majority (ϳ85%) of patients with ADPKD and are associated with a more severe clinical presentation and earlier onset of end-stage renal disease than the PKD2 phenotype (4). However, in all other aspects, PKD1 and PKD2 mutations produce virtually indistinguishable disease manifestations, indicating that the two proteins might function in a common signaling pathway involved in maintaining the terminally differentiated state of renal epithelial cells.TRPP2 is a 968-amino acid (aa) protein with six predicted transmembrane domains and is highly conserved among multicellular organisms and widely expressed in various tissues (2). Structural analyses indicate that TRPP2 contains several functional domains in its C-terminal tail. There are two Ca 2ϩ -binding sites (aa 680 -796) arranged in a typical and an atypical EF-hand motif, which could be involved in a Ca 2ϩ -mediated regulation of TRPP2 (6). An endoplasmic reticulum (ER) retention signal (aa 787-820) (7) and a coiled-coil domain (aa 839 -919), responsible for homo-and heterodimerization (8,9), are also present. Recently, it was reported that this coiled-coil domain was responsible for formation of a TRPP2 trimer that interacts with PKD1 in the plasma membrane (9).

Summary The inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) is a universal intracellular Ca2+-release channel. It is activated after cell stimulation and plays a crucial role in the initiation and propagation of the complex spatio-temporal Ca2+ signals that control cellular processes as different as fertilization, cell division, cell migration, differentiation, metabolism, muscle contraction, secretion, neuronal processing, and ultimately cell death. To achieve these various functions, often in a single cell, exquisite control of the Ca2+ release is needed. This review aims to highlight how protein kinases and protein phosphatases can interact with the IP3R or with associated proteins and so provide a large potential for fine tuning the Ca2+-release activity and for creating efficient Ca2+ signals in subcellular microdomains.

IRBIT is an IP3R [IP3 (inositol 1,4,5-trisphosphate) receptor]-binding protein that competes with IP3 for binding to the IP3R. Phosphorylation of IRBIT is essential for the interaction with the IP3R. The unique N-terminal region of IRBIT, residues 1-104 for mouse IRBIT, contains a PEST (Pro-Glu-Ser-Thr) domain with many putative phosphorylation sites. In the present study, we have identified a well-conserved PP1 (protein phosphatase-1)-binding site preceeding this PEST domain which enabled the binding of PP1 to IRBIT both in vitro and in vivo. IRBIT emerged as a mediator of its own dephosphorylation by associated PP1 and, hence, as a novel substrate specifier for PP1. Moreover, IRBIT-associated PP1 specifically dephosphorylated Ser68 of IRBIT. Phosphorylation of Ser68 was required for subsequent phosphorylation of Ser71 and Ser74, but the latter two sites were not targeted by PP1. We found that phosphorylation of Ser71 and Ser74 were sufficient to enable inhibition of IP3 binding to the IP3R by IRBIT. Finally, we have shown that mutational inactivation of the docking site for PP1 on IRBIT increased the affinity of IRBIT for the IP3R. This pinpoints PP1 as a key player in the regulation of IP3R-controlled Ca2+ signals.

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Cell-free (cf) DNA from plasma offers an easily obtainable material for BRAF mutation analysis for diagnostics and response monitoring. In this study, plasma-derived cfDNA samples from patients with progressing advanced cancers or malignant histiocytosis with known BRAF V600 status from formalin-fixed paraffinembedded (FFPE) tumors were tested using a prototype version of the Idylla BRAF Mutation Test, a fully integrated real-time PCRbased test with turnaround time about 90 minutes. Of 160 patients, BRAF V600 mutations were detected in 62 (39%) archival FFPE tumor samples and 47 (29%) plasma cfDNA samples. The two methods had overall agreement in 141 patients [88%; k, 0.74; SE, 0.06; 95% confidence interval (CI), 0.63-0.85]. Idylla had a sensitivity of 73% (95% CI, 0.60-0.83) and specificity of 98%