DLG1 polarity protein expression associates with the disease progress of low-grade cervical intraepithelial lesions

Human Discs large tumour suppressor (DLG1) participates in regulating cell polarity and proliferation, suggesting an important connection between epithelial organization and cellular growth control. However, it was demonstrated that DLG1 could acquire oncogenic attributes in some specific contexts. In this work, we evaluated the expression of DLG1 and its contribution to the progress of cervical lesions in order to investigate a potential role of this polarity protein in human oncogenic processes.We analyzed cervical biopsies from women with low-grade squamous intraepithelial lesion (LSIL) diagnosis (n = 30), for DLG1 expression by immunohistochemistry. These results were correlated with the clinical monitoring of the patients during a 24-month follow-up period. Our data indicate that while all LSIL patients with a DLG1 staining pattern similar to normal tissues are significantly more likely to regress (n = 23, Pattern I), all LSIL biopsy specimens showing a diffuse and intense DLG1 staining likely progress to high-grade lesions (n = 4, Pattern II). Finally, all persistent LSIL analyzed showed an undetermined DLG1 staining, with a diffuse distribution without a strong intensity (n = 3, Pattern III). We found a significant association between the expression pattern of DLG1 and the evolution of the lesion (p < 0.00001).This work contributes to the knowledge of DLG1 biological functions, suggesting that its expression may have an important role in the progression of early dysplastic cervical lesions, giving prognostic information.     

Expression and regulation of the renal Na/phosphate cotransporter NaPi-IIa in a mouse model deficient for the PDZ protein PDZK1

Inorganic phosphate (P_i) is reabsorbed in the renal proximal tubule mainly via the type-IIa sodium-phosphate cotransporter (NaPi-IIa). This protein is regulated tightly by different factors, among them dietary P_i intake and parathyroid hormone (PTH). A number of PDZ-domain-containing proteins have been shown to interact with NaPi-IIa in vitro, such as Na⁺/H⁺ exchanger-3 regulatory factor-1 (NHERF1) and PDZK1. PDZK1 is highly abundant in kidney and co-localizes with NaPi-IIa in the brush border membrane of proximal tubules. Recently, a knock-out mouse model for PDZK1 (Pdzk1^–/–) has been generated, allowing the role of PDZK1 in the expression and regulation of the NaPi-IIa cotransporter to be examined in in vivo and in ex vivo preparations. The localization of NaPi-IIa and other proteins interacting with PDZK1 in vitro [Na⁺/H⁺ exchanger (NHE3), chloride-formate exchanger (CFEX)/putative anion transporter-1 (PAT1), NHERF1] was not altered in Pdzk1^–/– mice. The abundance of NaPi-IIa adapted to acute and chronic changes in dietary P_i intake, but steady-state levels of NaPi-IIa were reduced in Pdzk1^–/– under a P_i rich diet. This was paralleled by a higher urinary fractional P_i excretion. The abundance of the anion exchanger CFEX/PAT1 (SLC26A6) was also reduced. In contrast, NHERF1 abundance increased in the brush border membrane of Pdzk1^–/– mice fed a high-P_i diet. Acute regulation of NaPi-IIa by PTH in vivo and by PTH and activators of protein kinases A, C and G (PKA, PKC and PKG) in vitro (kidney slice preparation) was not altered in Pdzk1^–/– mice. In conclusion, loss of PDZK1 did not result in major changes in proximal tubule function or NaPi-IIa regulation. However, under a P_i-rich diet, loss of PDZK1 reduced NaPi-IIa abundance indicating that PDZK1 may play a role in the trafficking or stability of NaPi-IIa under these conditions.An erratum to this article can be found at     

Differential interaction of the tSXV motifs of the NR1 and NR2A NMDA receptor subunits with PSD-95 and SAP97.

The NR1 and NR2 subunits of the N-methyl-D-aspartate (NMDA) receptor are encoded by distinct genes. In the rat brain, four C-terminal variants of the NR1 subunit (NR1-1 to NR1-4) are encoded by a single gene, and are generated by alternative splicing of the C1 and C2 exon cassettes, while four different genes encode the NR2 subunits (NR2 A-D). Functional NMDA receptors result from the heteromultimeric assembly of NR1 variants with distinct NR2 subunits. The NR2B subunit interacts with post-synaptic density protein 95 (PSD-95), SAP97 and members of the membrane-associated guanylate-like kinase (MAGUK) family of proteins. This interaction occurs through the binding of the C-terminal tSXV intracellular motif of the NR2B subunit to the N-terminal PDZ (PSD-95, discs-large, ZO-1) domains of the PSD-95 and SAP97 proteins. Both NR1-3 and NR1-4 also display a consensus C-terminal tSXV motif. Using the two-hybrid genetic system in yeast and site-directed mutagenesis, we compared the binding of the NR2A, NR1-3 and NR1-4 tSXV motifs with the PDZ domains of PSD-95 and SAP97. The main conclusions of the present report are that: (i) while NR2A displays a strong interaction with PSD-95 and SAP97, the NR1-3 and NR1-4 NMDA receptor subunits do not display any interaction despite the presence of tSXV motifs; (ii) the C-terminal tSXV motif of the NR2A subunit is mandatory but not sufficient for efficient interaction with the PSD-95 and SAP97 proteins; (iii) as yet unidentified upstream sequences of the receptor subunits determine whether the tSXV motifs will bind to the PSD-95 and SAP97 PDZ domains; (iv) different tSXV motifs elicit interactions of variable strengths; and (v) residues in positions -3 and -4 modulate the binding affinity of the C-terminal tSXV motifs. Using immunohistochemistry, we also compared the distribution of the PSD-95, NR2A and SAP97 proteins in adult rat brain, and we show that in the cortex, hippocampus and cerebellum, there is evidence for colocalization of these proteins.     

Endothelial cell specific adhesion molecule (ESAM) localizes to platelet–platelet contacts and regulates thrombus formation in vivo

Summary.  Background:  In resting platelets, endothelial cell specific adhesion molecule (ESAM) is located in alpha granules, increasing its cell surface expression following platelet activation. However, the function of ESAM on platelets is unknown. Objective:  To determine whether ESAM has a role in thrombus formation. Methods and results:  We found that following platelet activation ESAM localizes to the junctions between adjacent platelets, suggesting a role for this protein in contact-dependent events that regulate thrombus formation. To test this hypothesis we examined the effect of ESAM deletion on platelet function. In vivo , ESAM^−/− mice achieved more stable hemostasis than wild-type mice following tail transection, and developed larger thrombi following laser injury of cremaster muscle arterioles. In vitro , ESAM^−/− platelets aggregated at lower concentrations of G protein-dependent agonists than wild-type platelets, and were more resistant to disaggregation. In contrast, agonist-induced calcium mobilization, α_IIbβ₃ activation, alpha-granule secretion and platelet spreading, were normal in ESAM-deficient platelets. To understand the molecular mechanism by which ESAM regulates platelet activity, we utilized a PDZ domain array to identify the scaffold protein NHERF-1 as an ESAM binding protein, and further demonstrated that it associates with ESAM in both resting and activated platelets. Conclusions:  These findings support a model in which ESAM localizes to platelet contacts following platelet activation in order to limit thrombus growth and stability so that the optimal hemostatic response occurs following vascular injury.     

NMDA induces NOS 1 translocation to the cell membrane in NGF-differentiated PC 12 cells

Glutamatergic-mediated nitric oxide (NO) production occurs via the N-methyl-D-aspartic acid (NMDA) postsynaptic density protein 95 (PSD95)-neuronal nitric oxide synthase (NOS1) ternary complex. To determine whether NOS1 is targeted to the membrane subsequent to NMDA receptor activation, we examined the effect of NMDA on NOS1 subcellular localization in nerve growth factor (NGF) differentiated PC12 cells. No effect on cell viability was observed using a range of NMDA concentrations from 500 to 1000 microM. Within 3 min of stimulation with 750 microM NMDA, increased cytoplasmic NOS1 immunostaining was observed with rapid membrane staining thereafter. This was inhibited by NMDAR inhibition with MK801. This observation was confirmed using subcellular fractionation and immunoblotting. Using 4, 5-diaminofluorescein diacetate (DAF2-DA) staining and a diazotization assay, concurrent NO production was observed. When PC 12 cells were co-treated with either NMDA and N(6)-nitro-L-arginine methyl ester hydrochloride (L-NAME) or (5R, 10S)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a, d] cyclohepten-5, 10-imine hydrogen maleate (MK-801), nitric oxide (NO) generation was inhibited. Stimulation in a calcium-free medium did not increase NO levels. Although no evidence of cytotoxicity was observed utilizing either the MTT assay or measures of apoptosis within the maximal interval of NOS1 translocation, cell viability was reduced following 10 h of continuous NMDA exposure. While it has been shown that NMDA triggers NOS1 activation, these results indicate that NMDAR activation also mediates NOS1 targeting to the membrane. Our data validate that NGF-differentiated PC12 cells may be employed as a useful in vitro model to further study the regulation of NOS1 subsequent to NMDAR activation.     

Interaction of the epithelial Ca2+ channels TRPV5 and TRPV6 with the intestine- and kidney-enriched PDZ protein NHERF4

The epithelial Ca²⁺ channels TRPV5 and TRPV6 constitute the apical Ca²⁺ influx pathway in epithelial Ca²⁺ transport. PDZ proteins have been demonstrated to play a crucial role in the targeting or anchoring of ion channels and transporters in the apical domain of the cell. In this study, we describe the identification of NHERF4 (Na-P_i Cap2/IKEPP/PDZK2) as a novel TRPV5- and TRPV6-associated PDZ protein. NHERF4 was identified using two separate yeast two-hybrid screens with the carboxyl termini of TRPV5 and TRPV6 as bait. Binding of the carboxyl termini of TRPV5 and TRPV6 with NHERF4 was confirmed by GST pull-down assays using in-vitro-translated NHERF4 or lysates of Xenopus laevis oocytes expressing NHERF4. Furthermore, the interaction was confirmed by GST pull-down and co-immunoprecipitation assays using in-vitro-translated full-length TRPV5 and Xenopus oocytes or HEK293 cells co-expressing NHERF4 and TRPV5/TRPV6, respectively. The fourth PDZ domain of NHERF4 was sufficient for the interaction, although PDZ domain 1 also contributed to the binding. The binding site for NHERF4 localized in a conserved region in the carboxyl terminus of TRPV5 and was distinct from the binding site of the PDZ protein NHERF2. NHERF4 predominantly localized at the plasma membrane of X. laevis oocytes and HeLa cells. This localization was independent of the presence of TRPV5. Therefore, we hypothesize a role for this novel PDZ protein as a putative plasma membrane scaffold for the epithelial Ca²⁺ channels.     

Synaptic adhesion molecules and PSD-95

Synaptic adhesion molecules are known to participate in various steps of synapse development including initial contacts between dendrites and axons, formation of early synapses, and their maturation and plastic changes. Notably, a significant subset of synaptic adhesion molecules associates with synaptic scaffolding proteins, suggesting that they may act in concert to couple trans-synaptic adhesion to molecular organization of synaptic proteins. Here, we describe an emerging group of synaptic adhesion molecules that directly interact with the abundant postsynaptic scaffold PSD-95, which include neuroligins, NGLs, SALMs, and ADAM22, and discuss how these proteins and PSD-95 act together to regulate synaptic development. PSD-95 may be one of the central organizers of synaptic adhesion that recruits diverse proteins to sites of synaptic adhesion, promotes trans-synaptic signaling, and couples neuronal activity with changes in synaptic adhesion.     

国产与进口氨甲酰胆碱对豚鼠离体肠平滑肌作用的比较

观察了国产与进口氨甲酰胆碱对豚鼠离体回肠的兴奋作用,并计算其激动剂的激动参数PD_2值分别为5.93和6.13s。二者PO_2值相似,表明国产氨甲酰胆碱对离体豚鼠回肠平滑肌的兴奋作用已达到了进口氨甲酰胆碱的药效标准。     

通过配体文库研究GIPC2 PDZ配体结合特点及其相互作用蛋白

目的通过验证性筛选配体文库,获得GIPC2 PDZ结构域的配体结合特点,进而找到GIPC2的相互作用蛋白。方法 1)利用酵母双杂交的方法从已有的PDZ配体库中寻找与GIPC2的PDZ结构域配体结合特性;2)根据GIPC2的亚细胞定位和肿瘤相关功能再结合PDZ结构域结合序列的共同特征在蛋白质数据库中预测GIPC2的天然潜在配体;3)将天然潜在配体的C末端序列依次与GIPC2 PDZ结构域或GIPC2全长进行验证反应,从而得到阳性蛋白。结果 1)GIPC2 PDZ结构域的配体结合特性是C末端最后4个氨基酸为-X-S/T-X-V/L/I,是Ⅰ类PDZ配体;2)综合GIPC2的生物学特征和GIPC2 PDZ结构域的配体结合特点,在蛋白质数据库中预测得到47个天然潜在配体;3)将天然潜在配体的C末端序列克隆至酵母双杂交系统进行验证,最后得到10个确定的阳性蛋白。结论获得10个GIPC2相互作用蛋白。