14-3-3 proteins regulate cullin 7-mediated Eag1 degradation

BACKGROUND

Mutations in the human gene encoding the neuron-specific Eag1 (K_V10.1; KCNH1) potassium channel are linked to congenital neurodevelopmental diseases. Disease-causing mutant Eag1 channels manifest aberrant gating function and defective protein homeostasis. Both the E3 ubiquitin ligase cullin 7 (Cul7) and the small acid protein 14-3-3 serve as binding partners of Eag1. Cul7 mediates proteasomal and lysosomal degradation of Eag1 protein, whereas over-expression of 14-3-3 notably reduces Eag1 channel activity. It remains unclear whether 14-3-3 may also contribute to Eag1 protein homeostasis.

RESULTS

In human cell line and native rat neurons, disruptions of endogenous 14-3-3 function with the peptide inhibitor difopein or specific RNA interference up-regulated Eag1 protein level in a transcription-independent manner. Difopein hindered Eag1 protein ubiquitination at the endoplasmic reticulum and the plasma membrane, effectively promoting the stability of both immature and mature Eag1 proteins. Suppression of endogenous 14-3-3 function also reduced excitotoxicity-associated Eag1 degradation in neurons. Difopein diminished Cul7-mediated Eag1 degradation, and Cul7 knock-down abolished the effect of difopein on Eag1. Inhibition of endogenous 14-3-3 function substantially perturbed the interaction of Eag1 with Cul7. Further structural analyses suggested that the intracellular Per-Arnt-Sim (PAS) domain and cyclic nucleotide-binding homology domain (CNBHD) of Eag1 are essential for the regulatory effect of 14-3-3 proteins. Significantly, suppression of endogenous 14-3-3 function reduced Cul7-mediated degradation of disease-associated Eag1 mutant proteins.

CONCLUSION

Overall these results highlight a chaperone-like role of endogenous 14-3-3 proteins in regulating Eag1 protein homeostasis, as well as a therapeutic potential of 14-3-3 modulators in correcting defective protein expression of disease-causing Eag1 mutants.

Monogenic Causes in Familial Stroke Across Intracerebral Hemorrhage and Ischemic Stroke Subtypes Identified by Whole-Exome Sequencing

Whole exome sequencing (WES) has been used to detect rare causative variants in neurological diseases. However, the efficacy of WES in genetic diagnosis of clinically heterogeneous familial stroke remains inconclusive. We prospectively searched for disease-causing variants in unrelated probands with defined familial stroke by candidate gene/hotspot screening and/or WES, depending on stroke subtypes and neuroimaging features at a referral center. The clinical significance of each variant was determined according to the American College of Medical Genetics guidelines. Among 161 probands (mean age at onset 53.2 ± 13.7 years; male 63.4%), 33 participants (20.5%) had been identified with 19 pathogenic/likely pathogenic variants (PVs; WES applied 152/161 = 94.4%). Across subtypes, the highest hit rate (HR) was intracerebral hemorrhage (ICH, 7/18 = 38.9%), particularly with the etiological subtype of structural vasculopathy (4/4 = 100%, PVs in ENG, KRIT1, PKD1, RNF213); followed by ischemic small vessel disease (SVD, 15/48 = 31.3%; PVs in NOTCH3, HTRA1, HBB). In contrast, large artery atherosclerosis (LAA, 4/44 = 9.1%) and cardioembolism (0/11 = 0%) had the lowest HR. NOTCH3 was the most common causative gene (16/161 = 9.9%), presenting with multiple subtypes of SVD (n = 13), ICH (n = 2), or LAA (n = 1). Importantly, we disclosed two previously unreported PVs, KRIT1 p.E379* in a familial cerebral cavernous malformation, and F2 p.F382L in a familial cerebral venous sinus thrombosis. The contribution of monogenic etiologies was particularly high in familial ICH and SVD subtypes in our Taiwanese cohort. Utilizing subtype-guided hotspot screening and/or subsequent WES, we unraveled monogenic causes in 20.5% familial stroke probands, including 1.2% novel PVs. Genetic diagnosis may enable early diagnosis, management and lifestyle modification. Among 161 familial stroke probands, 33 (20.5%) had been identified pathogenic or likely pathogenic monogenic variants related to stroke. The positive hit rate among all subtypes was high in intracerebral hemorrhage (ICH) and ischemic small vessel disease (SVD). Notably, two previously unreported variants, KRIT1 p.E379* in a familial cerebral cavernous malformation and F2 p.F382L in familial cerebral venous sinus thrombosis, were disclosed. CVT cerebral venous thrombosis; HTN Hypertensive subtype; LAA large artery atherosclerosis; SV structural vasculopathy; U Undetermined.

FKBP51 mediates resilience to inflammation-induced anxiety through regulation of glutamic acid decarboxylase 65 expression in mouse hippocampus

Background

Inflammation is a potential risk factor of mental disturbance. FKBP5 that encodes FK506-binding protein 51 (FKBP51), a negative cochaperone of glucocorticoid receptor (GR), is a stress-inducible gene and has been linked to psychiatric disorders. Yet, the role of FKBP51 in the inflammatory stress-associated mental disturbance remained unclear.

Methods

Fkbp5-deficient (Fkbp5-KO) mice were used to study inflammatory stress by a single intraperitoneal injection of lipopolysaccharide (LPS). The anxiety-like behaviors, neuroimaging, immunofluorescence staining, immunohistochemistry, protein and mRNA expression analysis of inflammation- and neurotransmission-related mediators were evaluated. A dexamethasone drinking model was also applied to examine the effect of Fkbp5-KO in glucocorticoid-induced stress.

Results

LPS administration induced FKBP51 elevation in the liver and hippocampus accompanied with transient sickness. Notably, Fkbp5-KO but not wild-type (WT) mice showed anxiety-like behaviors 7 days after LPS injection (LPS-D7). LPS challenge rapidly increased peripheral and central immune responses and hippocampal microglial activation followed by a delayed GR upregulation on LPS-D7, and these effects were attenuated in Fkbp5-KO mice. Whole-brain [¹⁸F]-FEPPA neuroimaging, which target translocator protein (TSPO) to indicate neuroinflammation, showed that Fkbp5-KO reduced LPS-induced neuroinflammation in various brain regions including hippocampus. Interestingly, LPS elevated glutamic acid decarboxylase 65 (GAD65), the membrane-associated GABA-synthesizing enzyme, in the hippocampus of WT but not Fkbp5-KO mice on LPS-D7. This FKBP51-dependent GAD65 upregulation was observed in the ventral hippocampal CA1 accompanied by the reduction of c-Fos-indicated neuronal activity, whereas both GAD65 and neuronal activity were reduced in dorsal CA1 in a FKBP51-independent manner. GC-induced anxiety was also examined, which was attenuated in Fkbp5-KO and hippocampal GAD65 expression was unaffected.

Conclusions

These results suggest that FKBP51/FKBP5 is involved in the systemic inflammation-induced neuroinflammation and hippocampal GR activation, which may contribute to the enhancement of GAD65 expression for GABA synthesis in the ventral hippocampus, thereby facilitating resilience to inflammation-induced anxiety.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02517-8.

Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation

Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K⁺ channel are associated with neurodevelopmental diseases, indicating an important role of Eag1 during brain development. A disease-causing Eag1 mutation is linked to decreased protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The general mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K⁺ channels, however, remain unclear. By using yeast two-hybrid screening, we identified another E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), as a novel binding partner primarily interacting with the carboxyl-terminal region of Eag1. MKRN1 mainly interacts with ER-localized immature core-glycosylated, as well as nascent nonglycosylated, Eag1 proteins. MKRN1 promotes polyubiquitination and ER-associated proteasomal degradation of immature Eag1 proteins. Although both CUL7 and MKRN1 contribute to ER quality control of immature core-glycosylated Eag1 proteins, MKRN1, but not CUL7, associates with and promotes degradation of nascent, nonglycosylated Eag1 proteins at the ER. In direct contrast to the role of CUL7 in regulating both ER and peripheral quality controls of Eag1, MKRN1 is exclusively responsible for the early stage of Eag1 maturation at the ER. We further demonstrated that both CUL7 and MKRN1 contribute to protein quality control of additional disease-causing Eag1 mutants associated with defective protein homeostasis. Our data suggest that the presence of this dual ubiquitination system differentially maintains Eag1 protein homeostasis and may ensure efficient removal of disease-associated misfolded Eag1 mutant channels.

Neuronal Exosomes Secreted under Oxygen-Glucose Deprivation/Reperfusion Presenting Differentially Expressed miRNAs and Affecting Neuronal Survival and Neurite Outgrowth

Ischemia/reperfusion is a key feature of acute ischemic stroke, which causes neuron dysfunction and death. Exosomes, small extracellular vesicles produced by most cell types, are implicated in the mediation of cellular interactions with their environment. Here, we investigated the contents and functions of exosomes from neurons under ischemic reperfusion injury. First, rat cortical primary neuronal cell cultures were placed in an oxygen- and glucose-deprived (OGD) medium, followed by reperfusion in a normoxic conditioned medium (OGD/R) to mimic ischemia/reperfusion in vitro. The neuron-derived exosomes were harvested from the conditioned medium under normoxia and OGD/R. Through next-generation sequencing, exosomal miRNA expression levels in normoxic and OGD/R condition were compared. Their functional activity in terms of neuron viability and quantitative analysis of neurite outgrowth were examined. The expression levels of 45 exosomal miRNAs were significantly different between normoxic and OGD/R conditions. Bioinformatics analysis of dysregulated exosomal miRNAs identified multiple pathways involved in cell survival and death processes and neuronal signaling. Moreover, treatment with exosomes from OGD/R to cultured cortical neurons significantly impaired neuronal cell viability and reduced neurite outgrowth in terms of the number of primary or total neurites as well as length of primary neurites, compared with exosomes from normoxic conditions. miRNA-packed exosomes released by neurons under OGD/R challenge may contribute to post ischemic neuronal injury and provide further understanding of the effect of stressed neurons on neighboring neuronal functions.

CUL4-DDB1-CRBN E3 Ubiquitin Ligase Regulates Proteostasis of ClC-2 Chloride Channels: Implication for Aldosteronism and Leukodystrophy

Voltage-gated ClC-2 channels are essential for chloride homeostasis. Complete knockout of mouse ClC-2 leads to testicular degeneration and neuronal myelin vacuolation. Gain-of-function and loss-of-function mutations in the ClC-2-encoding human CLCN2 gene are linked to the genetic diseases aldosteronism and leukodystrophy, respectively. The protein homeostasis (proteostasis) mechanism of ClC-2 is currently unclear. Here, we aimed to identify the molecular mechanism of endoplasmic reticulum-associated degradation of ClC-2, and to explore the pathophysiological significance of disease-associated anomalous ClC-2 proteostasis. In both heterologous expression system and native neuronal and testicular cells, ClC-2 is subject to significant regulation by cullin-RING E3 ligase-mediated polyubiquitination and proteasomal degradation. The cullin 4 (CUL4)-damage-specific DNA binding protein 1 (DDB1)-cereblon (CRBN) E3 ubiquitin ligase co-exists in the same complex with and promotes the degradation of ClC-2 channels. The CRBN-targeting immunomodulatory drug lenalidomide and the cullin E3 ligase inhibitor MLN4924 promotes and attenuates, respectively, proteasomal degradation of ClC-2. Analyses of disease-related ClC-2 mutants reveal that aldosteronism and leukodystrophy are associated with opposite alterations in ClC-2 proteostasis. Modifying CUL4 E3 ligase activity with lenalidomide and MLN4924 ameliorates disease-associated ClC-2 proteostasis abnormality. Our results highlight the significant role and therapeutic potential of CUL4 E3 ubiquitin ligase in regulating ClC-2 proteostasis.

Defective Gating and Proteostasis of Human ClC-1 Chloride Channel: Molecular Pathophysiology of Myotonia Congenita

The voltage-dependent ClC-1 chloride channel, whose open probability increases with membrane potential depolarization, belongs to the superfamily of CLC channels/transporters. ClC-1 is almost exclusively expressed in skeletal muscles and is essential for stabilizing the excitability of muscle membranes. Elucidation of the molecular structures of human ClC-1 and several CLC homologs provides important insight to the gating and ion permeation mechanisms of this chloride channel. Mutations in the human CLCN1 gene, which encodes the ClC-1 channel, are associated with a hereditary skeletal muscle disease, myotonia congenita. Most disease-causing CLCN1 mutations lead to loss-of-function phenotypes in the ClC-1 channel and thus increase membrane excitability in skeletal muscles, consequently manifesting as delayed relaxations following voluntary muscle contractions in myotonic subjects. The inheritance pattern of myotonia congenita can be autosomal dominant (Thomsen type) or recessive (Becker type). To date over 200 myotonia-associated ClC-1 mutations have been identified, which are scattered throughout the entire protein sequence. The dominant inheritance pattern of some myotonia mutations may be explained by a dominant-negative effect on ClC-1 channel gating. For many other myotonia mutations, however, no clear relationship can be established between the inheritance pattern and the location of the mutation in the ClC-1 protein. Emerging evidence indicates that the effects of some mutations may entail impaired ClC-1 protein homeostasis (proteostasis). Proteostasis of membrane proteins comprises of biogenesis at the endoplasmic reticulum (ER), trafficking to the surface membrane, and protein turn-over at the plasma membrane. Maintenance of proteostasis requires the coordination of a wide variety of different molecular chaperones and protein quality control factors. A number of regulatory molecules have recently been shown to contribute to post-translational modifications of ClC-1 and play critical roles in the ER quality control, membrane trafficking, and peripheral quality control of this chloride channel. Further illumination of the mechanisms of ClC-1 proteostasis network will enhance our understanding of the molecular pathophysiology of myotonia congenita, and may also bring to light novel therapeutic targets for skeletal muscle dysfunction caused by myotonia and other pathological conditions.

Novel SCA19/22-associated KCND3 mutations disrupt human KV 4.3 protein biosynthesis and channel gating

Mutations in the human voltage-gated K⁺ channel subunit K_V 4.3-encoding KCND3 gene have been associated with the autosomal dominant neurodegenerative disorder spinocerebellar ataxia types 19 and 22 (SCA19/22). The precise pathophysiology underlying the dominant inheritance pattern of SCA19/22 remains elusive. Using cerebellar ataxia-specific targeted next-generation sequencing technology, we identified two novel KCND3 mutations, c.950 G>A (p.C317Y) and c.1123 C>T (p.P375S) from a cohort with inherited cerebellar ataxias in Taiwan. The patients manifested notable phenotypic heterogeneity that includes cognitive impairment. We employed in vitro heterologous expression systems to inspect the biophysical and biochemical properties of human K_V 4.3 harboring the two novel mutations, as well as two previously reported but uncharacterized disease-related mutations, c.1013 T>A (p.V338E) and c.1130 C>T (p.T377M). Electrophysiological analyses revealed that all of these SCA19/22-associated K_V 4.3 mutant channels manifested loss-of-function phenotypes. Protein chemistry and immunofluorescence analyses further demonstrated that these mutants displayed enhanced protein degradation and defective membrane trafficking. By coexpressing K_V 4.3 wild-type with the disease-related mutants, we provided direct evidence showing that the mutants instigated anomalous protein biosynthesis and channel gating of K_V 4.3. We propose that the dominant inheritance pattern of SCA19/22 may be explained by the dominant-negative effects of the mutants on protein biosynthesis and voltage-dependent gating of K_V 4.3 wild-type channel.

Ca(2+)-binding protein centrin 4 is a novel binding partner of rat Eag1 K(+) channels

Eag1 is neuron-specific K(+) channel abundantly expressed in the brain and retina. Subcellular localization and physiological analyses in neurons reveal that Eag1 may participate in Ca(2+)-signaling processes in the synapse. Here, we searched for rat Eag1 (rEag1)-binding proteins that may contribute to Ca(2+) regulation of the K(+) channel. Yeast two-hybrid screening identified centrin 4, a member of the centrin family of Ca(2+)-binding proteins. GST pull-down and immunoprecipitation assays in brain and retina lysates confirm the interaction of centrin with rEag1 in neurons. Centrin 4 binds to rEag1 in the absence of Ca(2+). Raising Ca(2+) concentration enhances the association efficiency of centrin 4 and rEag1, and is required for the suppression of rEag1 currents by centrin 4. Altogether, our data suggest that centrin 4 is a novel binding partner that may contribute to Ca(2+) regulation of rEag1 in neurons.

The Eag domain regulates the voltage-dependent inactivation of rat Eag1 K+ channels

Eag (Kv10) and Erg (Kv11) belong to two distinct subfamilies of the ether-à-go-go K+ channel family (KCNH). While Erg channels are characterized by an inward-rectifying current-voltage relationship that results from a C-type inactivation, mammalian Eag channels display little or no voltage-dependent inactivation. Although the amino (N)-terminal region such as the eag domain is not required for the C-type inactivation of Erg channels, an N-terminal deletion in mouse Eag1 has been shown to produce a voltage-dependent inactivation. To further discern the role of the eag domain in the inactivation of Eag1 channels, we generated N-terminal chimeras between rat Eag (rEag1) and human Erg (hERG1) channels that involved swapping the eag domain alone or the complete cytoplasmic N-terminal region. Functional analyses indicated that introduction of the homologous hERG1 eag domain led to both a fast phase and a slow phase of channel inactivation in the rEag1 chimeras. By contrast, the inactivation features were retained in the reverse hERG1 chimeras. Furthermore, an eag domain-lacking rEag1 deletion mutant also showed the fast phase of inactivation that was notably attenuated upon co-expression with the rEag1 eag domain fragment, but not with the hERG1 eag domain fragment. Additionally, we have identified a point mutation in the S4-S5 linker region of rEag1 that resulted in a similar inactivation phenotype. Biophysical analyses of these mutant constructs suggested that the inactivation gating of rEag1 was distinctly different from that of hERG1. Overall, our findings are consistent with the notion that the eag domain plays a critical role in regulating the inactivation gating of rEag1. We propose that the eag domain may destabilize or mask an inherent voltage-dependent inactivation of rEag1 K+ channels.

The subfamily-specific assembly of Eag and Erg K+ channels is determined by both the amino and the carboxyl recognition domains

A functional voltage-gated K(+) (Kv) channel comprises four pore-forming α-subunits, and only members of the same Kv channel subfamily may co-assemble to form heterotetramers. The ether-à-go-go family of Kv channels (KCNH) encompasses three distinct subfamilies: Eag (Kv10), Erg (Kv11), and Elk (Kv12). Members of different ether-à-go-go subfamilies, such as Eag and Erg, fail to form heterotetramers. Although a short stretch of amino acid sequences in the distal C-terminal section has been implicated in subfamily-specific subunit assembly, it remains unclear whether this region serves as the sole and/or principal subfamily recognition domain for Eag and Erg. Here we aim to ascertain the structural basis underlying the subfamily specificity of ether-à-go-go channels by generating various chimeric constructs between rat Eag1 and human Erg subunits. Biochemical and electrophysiological characterizations of the subunit interaction properties of a series of different chimeric and truncation constructs over the C terminus suggested that the putative C-terminal recognition domain is dispensable for subfamily-specific assembly. Further chimeric analyses over the N terminus revealed that the N-terminal region may also harbor a subfamily recognition domain. Importantly, exchanging either the N-terminal or the C-terminal domain alone led to a virtual loss of the intersubfamily assembly boundary. By contrast, simultaneously swapping both recognition domains resulted in a reversal of subfamily specificity. Our observations are consistent with the notion that both the N-terminal and the C-terminal recognition domains are required to sustain the subfamily-specific assembly of rat Eag1 and human Erg.

Comparison of robotic-assisted and conventional laparoscopy in the management of adnexal masses

STUDY OBJECTIVE

To compare the outcome of robotic-assisted laparoscopy vs conventional laparoscopy in the management of ovarian masses.

DESIGN

Retrospective cohort (Canadian Task Force classification II-3).

SETTING

Academic medical centre in the northeast United States.

PATIENTS

Retrospective medical record review of 71 consecutive patients with presumed benign ovarian masses.

INTERVENTION

Robotic-assisted laparoscopy in 30 patients with presumed benign ovarian masses was compared with conventional laparoscopy in 41 patients.

MEASUREMENTS AND MAIN RESULTS

Operative outcomes including operative time, estimated blood loss, length of hospital stay, and complications were recorded. Standard statistical analysis was used to compare the outcomes in the 2 groups. Mean (SD) operative time in the robotic group was 1.95 (0.63) hours, which was significantly longer than in the conventional laparoscopic group, 1.28 (0.83) hours (p = .04). Estimated blood loss in the robotic group was 74.52 (56.23) mL, which was not significantly different from that in the conventional laparoscopic group, 55.97 (49.18) mL. There were no significant differences in length of hospital stay between the robotic and conventional laparoscopic groups: 1.20 (0.78) days and 1.48 (0.63). Conversion to laparotomy was not necessary in either group of patients. Intraoperative and postoperative complications were similar between the 2 groups.

CONCLUSION

Robotic-assisted laparoscopy is a safe and efficient technique for management of various types of ovarian masses. However, conventional laparoscopy is preferred for management of ovarian masses because of shorter operative time. Prospective studies are needed to evaluate the outcomes of robotic-assisted laparoscopic management of benign and malignant ovarian neoplasms.

The punctate localization of rat Eag1 K+ channels is conferred by the proximal post-CNBHD region

Background

In mammals, Eag K⁺ channels (K_V10) are exclusively expressed in the brain and comprise two isoforms: Eag1 (K_V10.1) and Eag2 (K_V10.2). Despite their wide presence in various regions of the brain, the functional role of Eag K⁺ channels remains obscure. Here we address this question by characterizing the subcellular localization of rat Eag1 (rEag1) and rat Eag2 (rEag2) in hippocampal neurons, as well as determining the structural basis underlying their different localization patterns.

Results

Immunofluorescence analysis of young and mature hippocampal neurons in culture revealed that endogenous rEag1 and rEag2 K⁺ channels were present in both the dendrosomatic and the axonal compartments. Only rEag1 channels displayed a punctate immunostaining pattern and showed significant co-localization with PSD-95. Subcellular fractionation analysis further demonstrated a distinct enrichment of rEag1 in the synaptosomal fraction. Over-expression of recombinant GFP-tagged Eag constructs in hippocampal neurons also showed a significant punctate localization of rEag1 channels. To identify the protein region dictating the Eag channel subcellular localization pattern, we generated a variety of different chimeric constructs between rEag1 and rEag2. Quantitative studies of neurons over-expressing these GFP-tagged chimeras indicated that punctate localization was conferred by a segment (A723-R807) within the proximal post-cyclic nucleotide-binding homology domain (post-CNBHD) region in the rEag1 carboxyl terminus.

Conclusions

Our findings suggest that Eag1 and Eag2 K⁺ channels may modulate membrane excitability in both the dendrosomatic and the axonal compartments and that Eag1 may additionally regulate neurotransmitter release and postsynaptic signaling. Furthermore, we present the first evidence showing that the proximal post-CNBHD region seems to govern the Eag K⁺ channel subcellular localization pattern.

Lipopolysaccharide induces degradation of connexin43 in rat astrocytes via the ubiquitin-proteasome proteolytic pathway

The astrocytic syncytium plays a critical role in maintaining the homeostasis of the brain through the regulation of gap junction intercellular communication (GJIC). Changes to GJIC in response to inflammatory stimuli in astrocytes may have serious effects on the brain. We have previously shown that lipopolysaccharide (LPS) reduces connexin43 (Cx43) expression and GJIC in cultured rat astrocytes via a toll-like receptor 4-mediated signaling pathway. In the present study, treatment of astrocytes with LPS resulted in a significant increase in levels of the phosphorylated forms of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) -1, -2, and -3 for up to 18 h. An increase in nuclear transcription factor NF-κB levels was also observed after 8 h of LPS treatment and was sustained for up to 18 h. The LPS-induced decrease in Cx43 protein levels and inhibition of GJIC were blocked by the SAPK/JNK inhibitor SP600125, but not by the NF-κB inhibitor BAY11-7082. Following blockade of de novo protein synthesis by cycloheximide, LPS accelerated Cx43 degradation. Moreover, the LPS-induced downregulation of Cx43 was blocked following inhibition of 26S proteasome activity using the reversible proteasome inhibitor MG132 or the irreversible proteasome inhibitor lactacystin. Immunoprecipitation analyses revealed an increased association of Cx43 with both ubiquitin and E3 ubiquitin ligase Nedd4 in astrocytes after LPS stimulation for 6 h and this effect was prevented by SP600125. Taken together, these results suggest that LPS stimulation leads to downregulation of Cx43 expression and GJIC in rat astrocytes by activation of SAPK/JNK and the ubiquitin-proteasome proteolytic pathway.

Daidzein induces neuritogenesis in DRG neuronal cultures

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14-3-3θ is a binding partner of rat Eag1 potassium channels

The ether-à-go-go (Eag) potassium (K(+)) channel belongs to the superfamily of voltage-gated K(+) channel. In mammals, the expression of Eag channels is neuron-specific but their neurophysiological role remains obscure. We have applied the yeast two-hybrid screening system to identify rat Eag1 (rEag1)-interacting proteins from a rat brain cDNA library. One of the clones we identified was 14-3-3θ, which belongs to a family of small acidic protein abundantly expressed in the brain. Data from in vitro yeast two-hybrid and GST pull-down assays suggested that the direct association with 14-3-3θ was mediated by both the N- and the C-termini of rEag1. Co-precipitation of the two proteins was confirmed in both heterologous HEK293T cells and native hippocampal neurons. Electrophysiological studies showed that over-expression of 14-3-3θ led to a sizable suppression of rEag1 K(+) currents with no apparent alteration of the steady-state voltage dependence and gating kinetics. Furthermore, co-expression with 14-3-3θ failed to affect the total protein level, membrane trafficking, and single channel conductance of rEag1, implying that 14-3-3θ binding may render a fraction of the channel locked in a non-conducting state. Together these data suggest that 14-3-3θ is a binding partner of rEag1 and may modulate the functional expression of the K(+) channel in neurons.

The Roles of CD4+ T Cells in Tumor Immunity

Activation of CD8+ cytotoxic T cells has long been regarded as a major antitumor mechanism of the immune system. Emerging evidence suggests that CD4+ T cells are required for the generation and maintenance of effective CD8+ cytotoxic and memory T cells, a phenomenon known as CD4+ T-cell help. CD4+ T-cell help facilitates the optimal expansion, trafficking, and effector function of CD8+ T cells, thereby enhancing tumor destruction. In addition, a specialized subset of CD4+ T cells, CD4+CD25+ regulatory T cells (TRegs), effectively hampers anti-tumor immune responses, which has been proposed to be one of the major tumor immune evasion mechanisms. Here, we review recent advances in deciphering how anti-tumor immune responses are orchestrated by CD4+ T cells. We will also discuss the immunotherapeutic potential of CD4+ T-cell manipulation in anti-tumor immune response.

Distal end of carboxyl terminus is not essential for the assembly of rat Eag1 potassium channels

The assembly of four pore-forming α-subunits into tetramers is a prerequisite for the formation of functional K(+) channels. A short carboxyl assembly domain (CAD) in the distal end of the cytoplasmic carboxyl terminus has been implicated in the assembly of Eag α-subunits, a subfamily of the ether-à-go-go K(+) channel family. The precise role of CAD in the formation of Eag tetrameric channels, however, remains unclear. Moreover, it has not been determined whether other protein regions also contribute to the assembly of Eag subunits. We addressed these questions by studying the biophysical properties of a series of different rat Eag1 (rEag1) truncation mutants. Two truncation mutants without CAD (K848X and W823X) yielded functional phenotypes similar to those for wild-type (WT) rEag1 channels. Furthermore, nonfunctional rEag1 truncation mutants lacking the distal region of the carboxyl terminus displayed substantial dominant-negative effects on the functional expression of WT as well as K848X and W823X channels. Our co-immunoprecipitation studies further revealed that truncation mutants containing no CAD indeed displayed significant association with rEag1-WT subunits. Finally, surface biotinylation and protein glycosylation analyses demonstrated that progressive truncations of the carboxyl terminus resulted in aggravating disruptions of membrane trafficking and glycosylation of rEag1 proteins. Overall, our data suggest that the distal carboxyl terminus, including CAD, is dispensable for the assembly of rEag1 K(+) channels but may instead be essential for ensuring proper protein biosynthesis. We propose that the S6 segment and the proximal carboxyl terminus may constitute the principal subunit recognition site for the assembly of rEag1 channels.

Schisandrin enhances dendrite outgrowth and synaptogenesis in primary cultured hippocampal neurons

BACKGROUND

Schisandra chinensis, commonly used in Asia for tea material and traditional Chinese medicine, is presumed to enhance mental and intellectual functions. In this study, the effects and signalling mechanisms of a purified compound schisandrin, one of the lignan of Schisandra chinensis, on primary cultured hippocampal neurons were investigated.

RESULTS

Schisandrin treatment enhanced total dendritic length and branching complexity, both of which were significantly suppressed in the presence of specific blockers for calmodulin-dependent kinase II (CaMKII), protein kinase C epsilon (PKCε), and mitogen activated protein kinase kinase (MEK). Moreover, schisandrin induced calcium influx, and phosphorylation of CaMKII, PKCε, and MEK. Inhibition of CAMKII and PKCε attenuated the schisandrin-induced phosphorylation of PKCε and MEK, and the phosphorylation of MEK, respectively. Moreover, schisandrin also stimulated the phosphorylation of cyclic AMP responsive-element binding protein (CREB) at Ser-133, an effect that was blocked by KN93. In addition to its neuritogenic effects, schisandrin increased the numbers of postsynaptic density-95-positive and FM1-43-positive puncta in dendrites and synaptic boutons, respectively.

CONCLUSION

In hippocampal neurons, schisandrin exhibits neurotrophic properties that are mediated by the CaMKII-PKCε-MEK pathway.

Involvement of endoplasmic reticulum stress and activation of MAP kinases in beta-lapachone-induced human prostate cancer cell apoptosis

Beta-lapachone, an o-naphthoquinone, induces various carcinoma cells to undergo apoptosis, but the mechanism is poorly understood. In the present study, we found that the beta-lapachone-induced apoptosis of DU145 human prostate carcinoma cells was associated with endoplasmic reticulum (ER) stress, as shown by increased intracellular calcium levels and induction of GRP-78 and GADD-153 proteins, suggesting that the endoplasmic reticulum is a target of beta-lapachone. Beta-Lapachone-induced DU145 cell apoptosis was dose-dependent and accompanied by cleavage of procaspase-12 and phosphorylation of p38, ERK, and JNK, followed by activation of the executioner caspases, caspase-7 and calpain. However, pretreatment with the general caspase inhibitor, z-VAD-FMK, or calpain inhibitors, including ALLM or ALLN, failed to prevent beta-lapachone-induced apoptotic cell death. Blocking the enzyme activity of NQO1 with dicoumarol, a known NQO1 inhibitor, or preventing an increase in intracellular calcium levels using BAPTA-AM, an intracellular calcium chelator, substantially inhibited MAPK phosphorylation, abolished the activation of calpain, caspase-12 and caspase-7, and provided significant protection of beta-lapachone-treated cells. These findings show that beta-lapachone-induced ER stress and MAP kinase phosphorylation is a novel signaling pathway underlying the molecular mechanism of the anticancer effect of beta-lapachone.

Differential localization of rat Eag1 and Eag2 potassium channels in the retina

Despite of their wide expression in the brain, the precise neurophysiological role of rat Eag1 (rEag1) and Eag2 (rEag2) K(+) channels remains elusive. Our previous studies in hippocampal pyramidal neurons demonstrate a somatodendritic localization of rEag1 and rEag2 channels, suggesting that the two channel isoforms may contribute to setting the membrane excitability of somas and dendrites. Here, we aim to further characterize the cellular and subcellular localization patterns of rEag1 and rEag2 proteins by studying their laminar distribution in the retina. Confocal microscopic analyses of immunofluorescence data revealed that rEag1 and rEag2 K(+) channels exhibit distinct cellular expression pattern in the retina. rEag1 immunoreactivity was most prominent in the outer half of the inner plexiform layer, whereas strong rEag2 immunostain was found in the outer and inner segments of photoreceptor cells, the outer plexiform layer, and the inner nuclear layer. These results suggest that rEag1 and rEag2 K(+) channels may play a significant role in the transmission of electrical signals along the retinal neuronal circuits. We also performed double-labeling experiments to demonstrate that rEag1 and rEag2 are predominantly expressed in the somatodendritic compartment of retinal neurons. In addition, we presented evidence suggesting that rEag1 channels may be expressed in the GABAergic amacrine cell. Finally, based on their different immunostaining patterns over the inner region of the retina, we propose that compared to rEag2, rEag1 expression encompasses a significantly broader range of the somatodendritic compartment of the retinal ganglion cell.

Dominant-negative effects of episodic ataxia type 2 mutations involve disruption of membrane trafficking of human P/Q-type Ca2+ channels

Episodic ataxia type 2 (EA2) is an autosomal dominant neurological disorder associated with mutations in the gene encoding pore-forming alpha(1A) subunits of human P/Q-type calcium (Ca(V)2.1) channels. The exact mechanism of how mutant channels cause such clinical EA2 features as cerebellar dysfunctions, however, remains unclear. Our previous functional studies in Xenopus oocytes support the idea that EA2 mutants may exert prominent dominant-negative effects on wild-type Ca(V)2.1 channels. To further pursue the mechanism underlying this dominant-negative effect, we examined the effects of EA2 mutants on the subcellular localization pattern of GFP-tagged wild-type Ca(V)2.1 channels in HEK293T cells. In the presence of EA2 mutants, wild-type channels displayed a significant deficiency in membrane targeting and a concurrent increase in cytoplasm retention. Moreover, the cytoplasmic fraction of wild-type channels co-localized with an endoplasmic reticulum (ER) marker, suggesting that a significant amount of wild-type Ca(V)2.1 channels was trapped in the ER. This EA2 mutant-induced ER retention pattern was reversed by lowering the cell incubation temperature from 37 to 27 degrees C. We also inspected the effects of untagged EA2 mutants on the functional expression of GFP-tagged wild-type Ca(V)2.1 channels in HEK293T cells. Whole-cell current density of wild-type channels was diminished in the presence of EA2 mutants, which was also reversed by 27 degrees C incubation. Finally, biochemical analyses indicated that EA2 mutants did not significantly affect the protein expression level of wild-type channels. Taken together, our data suggest that EA2 mutants induce significant ER retention of their wild-type counterparts, thereby suppressing the functional expression of Ca(V)2.1 channels.

Anti-Thy-1 antibody-induced neurite outgrowth in cultured dorsal root ganglionic neurons is mediated by the c-Src-MEK signaling pathway

Our previous study has shown that anti-Thy-1 antibody promotes neurite outgrowth of cultured dorsal root ganglion (DRG) neurons in a protein kinase A (PKA)-dependent manner. The present study provided another intracellular signaling pathway for the neurotrophic effect of anti-Thy-1 antibody. In DMSO-treated control cells, Thy-1 was enriched in microdomain-like structures on cell membranes by immunofluorescence observation. Treatment of DRG neurons with anti-Thy-1 antibody not only stimulated neurite outgrowth, but also increased the branching complexity of the neurites in both small and large neurons. We have previously shown that anti-Thy-1 antibody causes a time-dependent activation of mitogen-activated protein kinase (MEK) and of cyclic AMP response-element binding protein (CREB). Here, anti-Thy-1 antibody elicited a transient activation of c-Src kinase, and the activation of c-Src kinase appeared occurring upstream of the activation of MEK and CREB, since pretreatment with the Src kinase inhibitor, PP2, effectively abolished the anti-Thy-1 antibody-induced neurite outgrowth and the phosphorylation of MEK and CREB. CREB phosphorylation might result in upregulation of certain neurite outgrowth-related proteins. We therefore conclude that anti-Thy-1 antibody activates the c-Src kinase-MEK-CREB cascade and overcomes the inhibitory effect of Thy-1 on neurite outgrowth in DRG neurons.

Role of PKA in the anti-Thy-1 antibody-induced neurite outgrowth of dorsal root ganglionic neurons

Thy-1 is highly expressed in the mammalian nervous system. Our previous study showed that addition of anti-Thy-1 antibody to cultured dorsal root ganglionic (DRG) neurons promotes neurite outgrowth. In this study, we identified a novel signaling pathway mediating this event. Treatment with function-blocking anti-Thy-1 antibodies enhanced neurite outgrowth of DRG neurons in terms of total neurite length, longest neurite length, and total neurite branching points. To elucidate the possible signal transduction pathway involved, activation of kinases was evaluated by Western blotting. Transient phosphorylation of protein kinase A (PKA) and mitogen-activated kinase kinase (MEK) was induced after 15 min of anti-Thy-1 antibody treatment. Pretreatment with a PKA inhibitor (PKI) or an MEK inhibitor, PD98059, significantly decreased the neurite outgrowth response triggered by anti-Thy-1 antibody, indicating the involvement of both kinases. In addition, anti-Thy-1 antibody treatment also induced transient phosphorylation of cyclic AMP-response element-binding protein (CREB) and this effect was also blocked by a PKI or PD98059. Furthermore, the fact that PKI abolished anti-Thy-1 antibody-induced MEK phosphorylation showed that PKA acts upstream of the MEK-CREB cascade. In summary, the PKA-MEK-CREB pathway is a new pathway involved in the neurite outgrowth-promoting effect of anti-Thy-1 antibody.

Selective enhancement of tonic inhibition by increasing ambient GABA is insufficient to suppress excitotoxicity in hippocampal neurons

Gamma-aminobutyric acid (GABA) activates synaptic GABA(A) receptors to generate inhibitory postsynaptic potentials. GABA also acts on extrasynaptic GABA(A) receptors, resulting in tonic inhibition. The physiological role of tonic inhibition, however, remains elusive. We explored the neurophysiological significance of tonic inhibition by testing whether selective activation of extrasynaptic GABA(A) receptors is sufficient to curb excitotoxicity. Tonic inhibition was selectively enhanced by increasing ambient GABA. In both acute hippocampal slices and cultured hippocampal neurons, boosting tonic inhibition alone is insufficient to withstand the hyper-excitability of hippocampal neurons induced by low-magnesium (Mg2+) baths. Furthermore, selective activation of extrasynaptic GABA(A) receptors resulted in no significant neuroprotective effects against glutamate or low-Mg2+-induced neuronal cell deaths. These data imply that under physiological conditions extrasynaptic GABA(A) receptors are optimally activated by ambient GABA and that a further increase in extracellular GABA concentration will not significantly enhance the effect of tonic inhibition on neuronal excitability.

Dominant-negative effects of human P/Q-type Ca2+ channel mutations associated with episodic ataxia type 2

Episodic ataxia type 2 (EA2) is an inherited autosomal dominant disorder related to cerebellar dysfunction and is associated with mutations in the pore-forming alpha(1A)-subunits of human P/Q-type Ca(2+) channels (Cav2.1 channels). The majority of EA2 mutations result in significant loss-of-function phenotypes. Whether EA2 mutants may display dominant-negative effects in human, however, remains controversial. To address this issue, five EA2 mutants in the long isoform of human alpha(1A)-subunits were expressed in Xenopus oocytes to explore their potential dominant-negative effects. Upon coexpressing the cRNA of alpha(1A)-WT with each alpha(1A)-mutant in molar ratios ranging from 1:1 to 1:10, the amplitude of Ba(2+) currents through wild-type (WT)-Cav2.1 channels decreased significantly as the relative molar ratio of alpha(1A)-mutants increased, suggesting the presence of an alpha(1A)-mutant-specific suppression effect. When we coexpressed alpha(1A)-WT with proteins not known to interact with Cav2.1 channels, we observed no significant suppression effects. Furthermore, increasing the amount of auxiliary subunits resulted in partial reversal of the suppression effects in nonsense but not missense EA2 mutants. On the other hand, when we repeated the same coinjection experiments of alpha(1A)-WT and mutant using a splice variant of alpha(1A)-subunit that contained a considerably shorter COOH terminus (i.e., the short isoform), no significant dominant-negative effects were noted until we enhanced the relative molar ratio to 1:10. Altogether, these results indicate that for human WT-Cav2.1 channels comprising the long-alpha(1A)-subunit isoform, both missense and nonsense EA2 mutants indeed display prominent dominant-negative effects.

Beauvericin activates Ca2+-activated Cl- currents and induces cell deaths in Xenopus oocytes via influx of extracellular Ca2+

Beauvericin is a mycotoxin that infects a wide variety of cereal grains. The toxicological importance of beauvericin is implicated by its cytotoxicity in animal and human cells, which has been suggested to result from an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)). Despite the fact that beauvericin may activate extracellular Ca(2+) influx, beauvericin-induced cell deaths has been suggested to be exclusively due to Ca(2+) release from internal Ca(2+) stores. We endeavored to elucidate the mechanism of beauvericin-induced [Ca(2+)](i) increase by studying the effects of beauvericin in Xenopus oocytes. By applying a -140-mV prepulse prior to a series of test pulses, we found that beauvericin induced small inward currents at -140 mV, followed by outwardly rectifying currents that displayed an apparent reversal potential close to the expected equilibrium potential of Cl(-). Both the inward and outward currents induced by beauvericin were blocked by niflumic acid, a specific blocker for Ca(2+)-activated Cl(-) currents (I(Cl,Ca)). Removal of extracellular Ca(2+), as well as perfusion of lanthanide, abrogated beauvericin-induced currents. Beauvericin also displayed prominent cytotoxic effects in Xenopus oocytes in a dose-dependent manner. In the absence of extracellular Ca(2+), cytotoxicity-induced by 10 and 30 microM, but not 50 microM, of beauvericin was significantly diminished. Our results are consistent with the idea that beauvericin induces extracellular Ca(2+) influx, which in turn activates I(Cl,Ca) and contributes to beauvericin-induced cell deaths in Xenopus oocytes.

Differential localization of rat Eag1 and Eag2 K+ channels in hippocampal neurons

Two isoforms of rat ether-a-go-go (Eag) K channels, rEag1 and rEag2, are widely expressed in many regions of the brain. The neurophysiological roles of these channels, however, are unclear. We addressed this issue by studying their subcellular localizations in hippocampal neurons. Immunofluorescence studies using markers for different compartments of neurons demonstrated a differential expression pattern of rEag1 and rEag2 K channels in the somatodendritic region. Furthermore, rEag1 K channels were in close proximity to synaptophysin and densin-180, but not GAD65. Our data suggest that both rEag1 and rEag2 K channels may play a pivotal role in the regulation of the excitability of dendrites and somas, and that rEag1 K channels may modulate the postsynaptic signaling of glutamatergic synapses.

Tanshinone IIA isolated from Salvia miltiorrhiza elicits the cell death of human endothelial cells

Tanshinone IIA, a major component extracted from the traditional herbal medicine, Salvia miltiorrhiza Bunge, is known to exhibit potent cytotoxicity against various human carcinoma cells in vitro. However, the mechanism by which tanshinone IIA produces this anti-tumor effect remains unknown. Since anti-neovascularization has generally been regarded as an effective strategy for anti-cancer therapy, we decided to investigate the mechanism underlying tanshinone IIA-mediated death of human endothelial cells. In this study, we demonstrate that tanshinone IIA elicits human endothelial cell death independent of oxidative stress. These events are partially calcium-dependent and actually dependent upon NAD(P)H: quinone oxidoreductase (NQO1) activity. Tanshinone IIA induces an increase in intracellular calcium, which triggers the release of cytochrome c, thus causing loss of the mitochondrial membrane potential (MMP), resulting in the subsequent activation of caspases. Blocking the induction of Ca2+ perturbation with BAPTA-AM partially rescued cells from tanshinone IIA-induced cytotoxicity. Additionally, blocking NQO1 activity with dicoumoral or inhibiting caspase activities with the general caspase inhibitor, z-VAD-fmk, prevented cell death induced by tanshinone IIA. Therefore, our results imply that tanshinone IIA-mediated cytotoxicity against human endothelial cells may occur through activation of NQO1, which induces a calcium imbalance and mitochondrial dysfunction, thus stimulating caspase activity.

Role of Thy-1 in in vivo and in vitro neural development and regeneration of dorsal root ganglionic neurons

We have examined the expression of Thy-1, an abundant glycosylphosphatidylinositol (GPI)-anchored glycoprotein, in dorsal root ganglia (DRG) and associated nerve fascicles, during postnatal development and following a nerve crush. The expression levels of Thy-1 in DRG neurons, dorsal roots, and central processes in spinal cord were rather low at postnatal day 2, and gradually increased as DRG neurons matured. During early development, the expression of Thy-1 within DRG neurons was low and equally distributed between plasma membrane and cytosol. With maturation, the staining intensities of Thy-1 in both the plasma membrane and the cytosol of DRG neurons became increased. We also studied Thy-1 expression in the regeneration of mature DRG neurons following the crush injury of sciatic nerve. Two days after the crush injury, Thy-1 expression dramatically decreased in the DRG neurons on the lesion side. Between 4 and 7 days after the injury, the expression of Thy-1 gradually increased and returned to a normal level 1 week after the sciatic nerve crush. The time course of the up-regulation of Thy-1 expression during regeneration matched that of the recovery of sensory functions, such as pain withdraw reflex, placing reflex, and the score of Basso-Beattie-Bresnahan Locomotor Rating Scale. Taken together, our results suggest that Thy-1 expression is developmentally regulated and is closely associated with the functional maturation of DRG neurons during both postnatal development and nerve regeneration. Furthermore, perturbation of Thy-1 function with anti-Thy-1 antibodies promoted neurite outgrowth from primary cultured DRG neurons, again confirming the inhibitory role of Thy-1 on neurite outgrowth.

Cross-linking of P-selectin glycoprotein ligand-1 induces death of activated T cells

Increasing evidence has shown that death signaling in T cells is regulated in a complicated way. Molecules other than death receptors can also trigger T-cell death. Here, we demonstrate for the first time that P-selectin glycoprotein ligand-1 (PSGL-1) or CD162 molecules cross-linked by an anti-PSGL-1 monoclonal antibody, TAB4, can trigger a death signal in activated T cells. In contrast to classic cell death, PSGL-1-mediated T-cell death is caspase independent. It involves translocation of apoptosis-inducing factor from mitochondria to nucleus and mitochondrial cytochrome c release. Ultrastructurally, both peripheral condensation of chromatin and apoptotic body were observed in PSGL-1-mediated T-cell death. Collectively, this study demonstrates a novel role for PSGL-1 in controlling activated T-cell death and, thus, advances our understanding of immune regulation.

Densin-180 forms a ternary complex with the (alpha)-subunit of Ca2+/calmodulin-dependent protein kinase II and (alpha)-actinin

Densin-180 is a transmembrane protein that is tightly associated with the postsynaptic density in CNS neurons and is postulated to function as a synaptic adhesion molecule. Here we report the identification of the alpha-subunit of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and alpha-actinin-4 as potential binding partners for the densin-180 intracellular segment. We demonstrate by yeast two-hybrid and biochemical assays that the intracellular portion of densin-180, the alpha-subunit of CaMKII (CaMKIIalpha), and alpha-actinin interact with each other at distinct binding sites and can form a ternary complex stabilized by multiple interactions. Densin-180 binds specifically to the association domain of CaMKIIalpha and does not bind with high affinity to holoenzymes of CaMKII that contain beta-subunit. The PDZ (PSD-95, DIg, Z0-1) domain of densin contributes to its binding to alpha-actinin. A distinct domain of alpha-actinin interacts with the kinase domains of both alpha- and beta-subunits of CaMKII. Autophosphorylation of CaMKII increases its affinity for densin-180 from an EC(50) of >1 micrometer to an EC(50) of <75-150 nM. In contrast, phosphorylation of densin-180 by CaMKII at serine-1397 only slightly decreases its affinity for CaMKII. The specific interaction of densin-180 with holoenzymes of CaMKII containing only alpha-subunit and the increased affinity of CaMKII for densin-180 after autophosphorylation suggest that densin-180 may be involved in localization of activated CaMKII synthesized in dendrites.

Androgen receptor gene mutations in 46,XY females with germ cell tumours

We present clinical findings and molecular characterization in two patients previously diagnosed as 46,XY female gonadal dysgenesis with germ cell tumour. Both patients showed a female general phenotype with unambiguously female external genitalia and primary amenorrhoea compatible with complete androgen insensitivity syndrome. The first patient, at the age of 31 years, developed a dysgerminoma measuring 8 x 13 x 10 cm in one abdominal testis. Genetic analysis revealed a single nucleotide substitution on exon 4 in the hormone-binding domain of the androgen receptor (AR) gene, resulting in a change of codon 681 GAG (glutamic acid) to AAG (lysine). The second patient, at the age of 17 years, developed a dysgerminoma measuring 12 x 10 x 7 cm in one abdominal testis and gonadoblastoma in the other testis. Genetic analysis showed a point mutation on exon 3 in the DNA-binding domain of the AR gene resulting in a change of codon 607 CGA (arginine) to CAA (glutamine). Arg607-Gln and Arg608-Lys point mutations in the DNA-binding domain of the AR gene have been associated with male breast cancer in partial androgen insensitivity syndrome. A codon 607 mutation in the DNA-binding domain of the AR gene in our patient 2 is associated with early development of germ cell tumour. We suggest regular molecular genetic analysis of the AR gene in 46,XY females with germ cell tumour and androgen insensitivity syndrome to detect differences in the specific regions of AR gene involved in early progression toward oncogenesis of the dysgenetic gonads.

Analysis of TSG101 tumour susceptibility gene transcripts in cervical and endometrial cancers

Carcinoma of the uterine cervix is a common malignancy among women that has been found to show loss of heterozygosity in the chromosome 11p. Recent studies have localized the TSG101 gene in this region, and also demonstrated a high frequency of abnormalities of this gene in human breast cancer. To determine the role of the TSG101 gene in the carcinogenesis of cervical and uterine carcinoma, 19 cases of cervical carcinoma and five cases of endometrial carcinoma, as well as nearby non-cancerous tissue from the same patients, and 16 blood samples from healthy persons as normal control were analysed by Southern blot analysis of genomic DNA, reverse transcription of the TSG101 mRNA followed by PCR amplification and sequencing of the products. We found that abnormal transcripts of the TSG101 gene were common both in cancerous or non-cancerous tissues of the uterus and cervix and in normal peripheral mononuclear cells. There was no genomic deletion or rearrangement in spite of the presence of abnormal transcripts, and no definite relationship between the abnormal transcripts and HPV infection was found. Although the frequency of abnormal transcripts was higher in cancerous than in non-cancerous tissue, normal peripheral mononuclear cells also had abnormal transcripts. Given these findings, the role of the TSG101 gene as a tumour-suppressor gene should be re-evaluated. Because some aberrant transcripts could be found at the first PCR reaction, we suggest that the aberrant transcripts might be the result of imperfect minor splicesome products.

Prognostic factors for an unsatisfactory primary methotrexate treatment of cervical pregnancy: a quantitative review

To determine the risks when the primary methotrexate (MTX) treatment of cervical pregnancy has an unsatisfactory outcome, we conducted a Medline search on relevant literature published from January 1983 to June 1997. The search yielded 28 publications of 48 cases of cervical pregnancy. These and four new cases from our institutions were used in our study. A cervical pregnancy that presented with a serum beta-human chorionic gonadotrophin concentration of > or = 10,000 mIU/ml [odds ratio (OR) 10.82, 95% confidence interval (CI) 2.59, 45.14], gestational age at > or = 9 weeks (OR 6.44, 95% CI 1.46, 28.52), embryonic cardiac activity (OR 14.29, 95% CI 2.95, 76.92), and crown-rump length of >10 mm (OR 13.33, 95% CI 1.46, 120.48) was considered to be associated with a higher unsatisfactory rate of primary MTX treatment. A concomitant feticide was found to enhance the therapeutic effect of MTX treatment if embryonic cardiac activity was evident (OR 0.13, 95% CI 0.02, 0.68). Administration of a high dose of MTX did not seem to be more effective than a lower one. Our findings supported some previous observations and, more importantly, provided useful clinical information in selecting appropriate candidates for MTX treatment in cases of cervical pregnancy.

Thy-1 is a component common to multiple populations of synaptic vesicles

Thy-1, a glycosylphosphatidylinositol-linked integral membrane protein of the immunoglobulin superfamily, is a component of both large dense-core and small clear vesicles in PC12 cells. A majority of this protein, formerly recognized only on the plasma membrane of neurons, is localized to regulated secretory vesicles. Thy-1 is also present in synaptic vesicles in rat central nervous system. Experiments on permeabilized PC12 cells demonstrate that antibodies against Thy-1 inhibit the regulated release of neurotransmitter; this inhibition appears to be independent of any effect on the Ca2+ channel. These findings suggest Thy-1 is an integral component of many types of regulated secretory vesicles, and plays an important role in the regulated vesicular release of neurotransmitter at the synapse.

Enlarged cisterna magna in the third trimester as a clue to fetal trisomy 18

Six of 19 fetuses with trisomy 18 confirmed by late karyotyping in the third trimester were found to have an enlarged cisterna magna (10 mm or more). For trisomy 18 conceptuses, there is a significant excess of females in both fetuses and livebirths; however, we found this ratio to be reversed in the third-trimester trisomy 18 fetuses with an enlarged cisterna magna (5 males vs. 1 female), indicating males are more likely to have this associated defect. Each of the 6 cases was associated with other trisomy markers including intrauterine growth retardation and polyhydramnios. Since a significant proportion of pregnancies may escape early prenatal care and some potentially detectable fetal abnormalities may be missed on early ultrasound and/or by maternal serum screenings, prenatal detection of an enlarged cisterna magna associated with intrauterine growth retardation and/or polyhydramnios in late gestation should prompt complete genetic counseling, rapid karyotyping and a careful search for other congenital anomalies.

Perinatal features of omphalocele-exstrophy-imperforate anus-spinal defects (OEIS complex) associated with large meningomyeloceles and severe limb defects

Omphalocele-Exstrophy-Imperforate anus-Spinal defects (OEIS complex), a combination of omphalocele, exstrophy of the bladder, an imperforate anus and spinal defects, arises from a single localized defect in the early development of the mesoderm that will later contribute to infraumbilical mesenchyme, cloacal septum, and caudal vertebrae. In this report, we document the perinatal features of two cases of OEIS complex associated with meningomyeloceles and severe lower limb defects, and discuss the prenatal diagnosis, inheritance, and differential diagnosis of this association of malformations. Although long-term survival can be achieved by successful corrective surgery, the associated structural defects such as large meningomyelocele and severe limb aplasia or hypoplasia, as seen in our patient, can influence the patient's quality of life. We would like to emphasize that an accurate prenatal diagnosis of OEIS complex and associated malformations is important for the detailed counseling of the family as well as appropriate perinatal management by the obstetricians, pediatric surgeons, urologists, neurosurgeons, and neonatologists.

Cervical cancer in young women in Taiwan: prognosis is independent of papillomavirus or tumor cell type

The objective of this study was to address the hypotheses that younger patients with cervical cancer have a uniquely worse clinical outcome and/or are more likely to have adverse tumor cell types or specific human papillomaviruses (HPV). Cases of stage Ib-IIa cervical cancer among women 35 years of age or younger (82) and over 35 (54) were analyzed and compared with respect to the following: (1) histologic type (squamous vs nonsquamous), (2) human papillomavirus (HPV) type via polymerase chain reaction, and (3) clinical parameters, including tumor size, nodal metastases, and recurrence/persistence. Patients 35 years of age or younger had a survival similar (71.2% vs 72.4%) to that of older women from the same institution. In the younger group, outcome was not correlated with the presence or absence of HPV or HPV type. Nonsquamous carcinomas, including adenocarcinoma and small cell carcinoma, were strongly associated with HPV18, were more prevalent in the younger group, and had a slightly higher risk of recurrence/persistence; however, these differences were not significant and 71% of the recurrences were squamous cell carcinomas. Thus, in young Taiwanese women with stage Ib-IIa cervical cancer, the majority of deaths cannot be attributed to a specific HPV type or unique tumor morphology.

Selective localization and regulated release of calcitonin gene-related peptide from dense-core vesicles in engineered PC12 cells

Introduction of the gene for calcitonin into the neuroendocrine PC12 cell line resulted in the expression of the neuronal-specific splice product, calcitonin gene-related peptide (CGRP). Expression of this neuropeptide did not require treatment of the PC12 cells with NGF. By all available criteria, including biochemical, immunological, and morphological analysis, we have determined that the CGRP in stably transfected PC12 cells is sorted selectively into the large, dense-core catecholamine-containing secretory vesicles. Conversely, the CGRP is excluded from the small, synaptophysin-rich vesicles present in the same cells. Stimulation conditions that trigger the release of catecholamines cause a parallel burst in the release of CGRP. In all these respects, the engineered PC12 cells process the foreign CGRP in a manner similar to that seen in spinal motor neurons in vivo. These results indicate that this small (37 amino acids) peptide contains sorting information sufficient for targeting to large, dense-core vesicles in heterologous cells, placing very narrow constraints on the possible location of sorting signals. In addition, this CGRP-expressing cell line opens the possibility of studying the physiological role of CGRP in the establishment and maintenance of neuromuscular contacts.

Treatment of cervical pregnancy with methotrexate

OBJECTIVES

To review our experience with early ultrasonographic diagnosis and fertility-preserving complete medical treatment of cervical pregnancy.

METHODS

From January 1989 to December 1994, 11 cases of cervical pregnancy diagnosed by ultrasonography and treated with methotrexate were evaluated. Patients were treated as follows: systemic administration of methotrexate with leucovorin rescue, a single dose of 50 mg of methotrexate intramuscular injection, or transvaginal ultrasonographically-guided intra-amniotic instillation of 50 mg of methotrexate.

RESULTS

The mean age of these patients was 33.3 +/- 6.2 years and gestational age at diagnosis ranged from 32 to 73 days. The maximal serum beta-hCG measured was 135,000 mIU/ml, and the time required for return to normal levels ranged from 20 to 157 days. The ectopic gestation was successfully ablated in all cases, and none required hysterectomy.

CONCLUSION

If a cervical pregnancy is present and diagnosed early, methotrexate treatment, administered either systemically or locally, is effective as the definitive therapy.

Pelvic abscess caused by Salmonella: a case report

We report a case of a 28-year-old woman, with no history of sexual activity, who developed a cul-de-sac abscess and bilateral salpingitis caused by Salmonella group C1. This paper documents our limited experience with such an unusual event and suggests that gastrointestinal pathogens should be considered as potential etiologic organisms in patients presenting with pelvic infection and gastroenteritis.

Sonographic and clinical findings of granulosa cell tumor

BACKGROUND

Granulosa cell tumor (GCT) accounts for roughly 1.5% of all ovarian neoplasms and 5-10% of ovarian cancers. GCT, which may have profound end-organ effects, has attracted a significant amount of attention despite its rarity. This tumor is rare, and difficult to diagnose before operation. Until now, no specific sonographic findings have been reported.

METHODS

Twelve cases of pathologically proven GCTs were diagnosed from June 1985 to March 1993. Nine of those cases had preoperative sonographic pictures taken.

RESULTS

Eight out of the nine cases tested exhibited a complex multicystic sonographic pattern. For a case evaluated by a transvaginal color and pulsed Doppler assessment, the blood vessels located in the central part with diffuse dispersed vascular arrangement were found to have a resistance index of 0.38 and a pulsatility index of 0.50. The most common complaints of our patients were postmenopausal bleeding and lower abdominal pain.

CONCLUSIONS

We conclude that complex multicystic sonographic features observed by high-resolution ultrasonography, in conjuction with a high preoperative estradiol level and clinical symptoms, may help to establish a preoperative diagnosis of GCT.