[A preliminary study on the efficacy and safety of a new type of trabeculotome tunnelling trabeculoplasty for open-angle glaucoma]

Objective: To compare the efficacy and safety of trabeculotome tunnelling trabeculoplasty and gonioscopy-assisted transluminal trabeculotomy (GATT) in the treatment of open-angle glaucoma. Methods: A prospective randomized controlled study. The patients with open-angle glaucoma diagnosed in the ophthalmology center of Beijing Tongren Hospital affiliated to Capital Medical University from January to July 2022 were collected and divided into GATT group (undergoing GATT) and 3T group (undergoing 3T operation) using a random number table. Intraocular pressure (IOP) was recorded for both groups at 1 day, 1 week, 1 month, and 3 months after the operation, and the types and quantities of anti-glaucoma drugs used, postoperative complications, and surgical success rate were compared. Normal distribution measurement data were analyzed using independent sample t-tests, non-normal distribution measurement data were analyzed using non-parametric tests, and counting data were analyzed using chi-square tests. Results: This study included 35 patients (43 eyes), consisting of 27 males and 8 females, with an average age of (43.0±14.3) years. There were 21 patients (23 eyes) in the GATT group and 19 patients (20 eyes) in the 3T group. The maximum IOP without anti-glaucoma drugs before surgery, the highest IOP with the maximum number of anti-glaucoma drugs, and the IOP at 3 months after surgery in the GATT group were (33.5±9.1), (22.2±6.1), and (16.0±3.1) mmHg (1 mmHg=0.133 kPa), respectively. The corresponding values for the 3T group were (35.2±7.8), (21.5±6.8), and (16.1±2.0) mmHg. After surgery, the IOP in both groups was lower than before surgery, with a statistically significant difference (P<0.05) and no significant difference between the two groups (P>0.05). In the 3 months following surgery, 13 eyes in the GATT group and 11 eyes in the 3T group received more than two types of anti-glaucoma drugs, with no significant difference between the two groups (P>0.05). Three months after surgery, the complete and conditional success rates of the GATT group were 14/18 and 16/18, respectively, and those of the 3T group were 12/15 and 13/15, respectively, with no significant difference between the two groups (P>0.05). The incidence of hyphema, ciliary detachment, and shallow anterior chamber 1 day after surgery was 91%(21/23), 35%(8/23), and 30%(7/23), respectively, in the GATT group and 55%(11/20), 5%(1/20), and 0 in the 3T group, with a statistically significant difference between the two groups (P<0.05). Conclusion: 3T and GATT have similar success rates in the treatment of open-angle glaucoma. However, compared with GATT, 3T has fewer complications and is considered to be safer. (This article was published ahead of print on the Online-First Publishing Platform for Excellent Scientific Researches of Chinese Medical Association Publishing House on February 28, 2023).

[Silencing SIRT1 reduces 5-fluorouracil resistance of cholangiocarcinoma cells by inhibiting the FOXO1/Rab7 autophagy pathway]

OBJECTIVE

To investigate the mechanism by which SIRT1 silencing reduces 5-fluorouracil (5-FU) resistance of cholangiocarcinoma cells and the role of FOXO1/Rab7 autophagy pathway in mediating this effect.

METHODS

Human cholangiocarcinoma HCCC-9810 cells were treated with 50, 100, 150, and 200 μg/mL 5-FU to construct a 5-FU-resistant cell model, whose expressions of SIRT1, FOXO1 and Rab7 were detected with immunofluorescence assay, Western blotting and RTqPCR, and the expression levels of autophagy related proteins (Beclin1, LC3, and p62) were detected with Western blotting. The 5-FU resistant cells were transfected with a SIRT1 siRNA, and the changes in 5-Fu resistance and migration ability of the cells were evaluated using CCK-8 assay and wound healing assay; The changes in FOXO1 and Rab7 mRNA levels and protein expressions of SIRT1, FOXO1, Rab7, Beclin1, LC3 and P62 were detected with RT-qPCR and Western blotting.

RESULTS

Treatments with 5-FU at 50, 100, 150, and 200 μg/mL all inhibited the proliferation of HCCC-9810 cells. Immunofluorescence assay revealed significantly enhanced SIRT1 expression in 5-FU-resistant HCC-9810 cells, and Western blotting also showed significantly up-regulated protein expressions of SIRT1, Rab7, P62, FOXO1 and Beclin 1 (P < 0.001) and an increased LC3II/LC3I ratio in the cells (P < 0.001). The mRNA levels of SIRT1, Rab7 and FOXO1 were also up-regulated in 5-Fu-resistant cells (P < 0.05). SIRT1 silencing significantly attenuated 5-FU resistance and migration ability of HCCC-9810 cells, and obviously decreased the protein expressions of SIRT1, Rab7, P62, FOXO1 and Beclin1 and the LC3II/LC3I ratio as well (P < 0.001). FOXO1 and Rab7 mRNA levels were significantly decreased in 5-FU-resistant HCC-9810 cells after SIRT1 silencing (P < 0.05).

CONCLUSION

Silencing SIRT1 attenuates 5-FU resistance in HCC-9810 cells by inhibiting the activation of the FOXO1/Rab7 autophagy pathway.

Warming reduced flowering synchrony and extended community flowering season in an alpine meadow on the Tibetan Plateau

The timing of phenological events is highly sensitive to climate change, and may influence ecosystem structure and function. Although changes in flowering phenology among species under climate change have been reported widely, how species-specific shifts will affect phenological synchrony and community-level phenology patterns remains unclear. We conducted a manipulative experiment of warming and precipitation addition and reduction to explore how climate change affected flowering phenology at the species and community levels in an alpine meadow on the eastern Tibetan Plateau. We found that warming advanced the first and last flowering times differently and with no consistent shifts in flowering duration among species, resulting in the entire flowering period of species emerging earlier in the growing season. Early-flowering species were more sensitive to warming than mid- and late-flowering species, thereby reducing flowering synchrony among species and extending the community-level flowering season. However, precipitation and its interactions with warming had no significant effects on flowering phenology. Our results suggest that temperature regulates flowering phenology from the species to community levels in this alpine meadow community, yet how species shifted their flowering timing and duration in response to warming varied. This species-level divergence may reshape flowering phenology in this alpine plant community. Decreasing flowering synchrony among species and the extension of community-level flowering seasons under warming may alter future trophic interactions, with cascading consequences to community and ecosystem function.

Effect of Hypoxic-Ischemic Brain Injury in Neonatal Rats on Behavioral Parameters and Expression of CDK8 in the Brain Tissue

Behavioral changes in newborn 3-day-old rats (n=44) with modeled hypoxic-ischemic brain injury (HIBI) were observed, and the expression of CDK8 in brain tissues was detected to clarify the significance of CDK8. In 30 min, 3 h, and 3 days after HIBI, the left (ischemic) hemisphere was taken for examination. In 3 days after HIBI, the rat pups were examined in the behavioral tests. In rat pups with HIBI, changes of CDK8 expression were detected by Western blotting and real-time PCR and changes in the righting reflex and forelimb grip strength test (p<0.05) were revealed in comparison with sham-operated animals. The expression of CDK8 increased 30 min after HIBI and decreased in 3 h and 3 days. Hypoxia and ischemia of the left brain may affect locomotion, but not sensation. Since CDK8 is involved in the immune response after cerebral hypoxia and ischemia, this kinase can be used as an early diagnostic index.

LncRNA INHBA-AS1 promotes colorectal cancer cell proliferation by sponging miR-422a to increase AKT1 axis

OBJECTIVE

In recent years, long non-coding RNAs (lncRNAs) have emerged for regulating the development, as well as progression in colorectal cancer (CRC), which assists in finding new targets for CRC treatment. A previous study indicated that INHBA-AS1 promotes oral squamous cell progression by sponging miR-143-3p. However, the exact function possessed by lncRNA INHBA-AS1 in CRC development remains unclear.

PATIENTS AND METHODS

The expression level of INHBA-AS1 in CRC tissues and cell lines was determined by qRT-PCR. The functional role of INHBA-AS1 in CRC was investigated by a series of in vitro assays. RNA immunoprecipitation (RIP), bioinformatics analysis was utilized to explore the potential mechanisms of INHBA-AS1.

RESULTS

The present study identified INHBA-AS1 as a kind of lncRNA with high expression in CRC tissues and cells. Functionally, NHBA-AS1 downregulation in CRC cells suppressed CRC cell proliferation as well as colony formability. Mechanistically, INHBA-AS1/miR-422a/AKT1 established the ceRNA network to regulate MMP-2, -7, -9 expressions that participated the modulation of CRC progression.

CONCLUSIONS

In summary, LncRNA INHBA-AS1 contributes to CRC progression through AKT1 pathway, and provides a new mechanism to regulate CRC development, as well as a potential target for treating CRC.

MiR-302b Suppresses Tumor Metastasis by Targeting Frizzled 6 in OSCC

Oral squamous cell carcinoma (OSCC) accounts for approximately 90% of malignant epithelial tumors of the oral and maxillofacial region. OSCC has high rate of metastasis and poor prognosis. Tobacco and/or alcohol consumption and human papillomavirus infection are relatively exact susceptibility factors for OSCC, but the specific process of oral mucosal carcinogenesis and progression is very complicated. microRNA-302b (miR-302b) could regulate various characteristics of many tumor cells, such as proliferation and apoptosis, but its role and mechanism in OSCC have not been reported. This research aims to study the effect of miR-302b on the invasion and migration ability of OSCC and the mechanism by which it functions as well as to identify new prognostic indicators and therapeutic targets for OSCC patients. Functional studies showed that the miR-302b level was negatively correlated with the invasion and migration ability of OSCC. The studies also showed that the overexpression of miR-302b could attenuate the invasion and migration ability of OSCC cells and reduce lymphangiogenesis and the lung metastasis rate of OSCC cells in a mouse model. Mechanistic studies were performed by quantitative polymerase chain reactions, luciferase assays, and RNA pull-down experiments. The results verified that frizzled class receptor 6 (FZD6) is a target gene of miR-302b in OSCC that could promote cell invasion and migration. Clinical studies demonstrate that the protein expression level of FZD6 was higher in OSCC and metastatic lymph nodes than in normal oral mucosa epithelium. Taken together, these data showed that miR-302b could inhibit the invasion and migration ability of OSCC cells by targeting and downregulating FZD6, thereby inhibiting OSCC metastasis. As a new target gene of miR-302b, FZD6 has the potential to become a prognostic and therapeutic target for OSCC patients.

[Predictive factors of pathological complete response after neoadjuvant chemoradiotherapy for middle-low rectal cancer]

Objective: To explore the predictive factors of pathological complete response (pCR) after neoadjuvant chemoradiotherapy for middle-low rectal cancer. Methods: A case-control study was conducted. The inclusion criteria were as follows: (1) colonoscopy, digital examination or magnetic resonance imaging (MRI) showed a distance from the lower edge of the tumor to the dentate line of no more than 10 cm; (2) complete clinicopathological data were available; (3) preoperative biopsy revealed adenocarcinoma; (4) preoperative pelvic MRI or endorectal ultrasonography was performed; (5) no distant metastasis was found. Exclusion criteria: (1) preoperative radiotherapy and chemotherapy were not administrated according to the standard; (2) simultaneous multiple primary cancer and familial adenomatous polyposis were observed. According to the above criteria, clinicopathological data of 245 patients with middle-low rectal cancer undergoing preoperative neoadjuvant chemoradiotherapy in Changhai Hospital of Navy Medical University from January 2012 to December 2019 were retrospectively collected. Univariate analysis and multivariate logistic analysis were used to identify the clinical factors predicting pCR. pCR is defined as complete disappearance of cancer cells under the microscope in cancer specimens (including lymph nodes) after neoadjuvant chemoradiotherapy. Results: A total of 72 patients with pCR were enrolled in this study. Univariate analysis showed that preoperative T stage, tumor circumference, tumor morphology, carbohydrate antigen (CA) 19-9, interval between the end of neoadjuvant therapy and operation were associated with pCR (all P<0.05). The above 5 variables were included in multivariate logistic analysis and the results revealed that the T stage (OR=5.743, 95% CI: 2.416-13.648, P<0.001), tumor circumference (OR=7.754, 95% CI: 3.822-15.733, P<0.001), tumor morphology (OR=0.264, 95% CI: 0.089-0.786, P=0.017) and the interval between the end of neoadjuvant therapy and operation (OR=0.303, 95% CI: 0.147-0.625, P=0.001) were independent predictive factors of pCR, while CA 19-9 level was not an independent factor (OR=1.873, 95% CI:0.372-9.436, P=0.447). Conclusion: By knowing the clinical features of preoperative T stage, tumor circumference, tumor morphology and the interval between neoadjuvant chemoradiotherapy and operation, patients with higher likelyhood of pCR after neoadjuvant chemoradiotherapy may be identified.

Polymorphisms in lncRNA PTENP1 and the risk of oral squamous cell carcinoma in a Chinese population

OBJECTIVE

PTENP1, a long noncoding RNA, has previously been reported to be involved in tumorigenesis and cancer progression. The relationship between PTENP1 and susceptibility tumors is reported, while, an association of PTENP1 with the risk of oral squamous cell carcinoma (OSCC) in Chinese population is lacked. This research is designed to investigate the association of PTENP1 with susceptibility of OSCC.

PATIENTS AND METHODS

In this research, TaqMan technology was used to test genotype in 342 OSCC patients and 711 healthy controls, so as to analyze the association between PTENP1 polymorphisms (rs7853346 rs865005 and rs10971638) and susceptibility of oral squamous cell carcinoma.

RESULTS

The results of this research showed that rs7853346 [Additive model: Adjusted odds ratio (OR) = 0.81, 95% confidence interval (CI) = 0.66-0.99] was related to the OSCC risk. It was not found that the other two sites were associated with the susceptibility of OSCC.

CONCLUSIONS

This research indicated that rs7853346 is statistically correlated with the OSCC risk.

Rapid specific and visible detection of porcine circovirus type 3 using loop-mediated isothermal amplification (LAMP)

In this study, a rapid and specific assay for the detection of porcine circovirus type 3 (PCV3) was established using loop-mediated isothermal amplification (LAMP). Four primers were specifically designed to amplify PCV3. The LAMP assay was effectively optimized to amplify PCV3 by water bath at 60°C for 60 min. The detection limit was approximately 1 × 10¹ copy in this LAMP assay. Compared to porcine circovirus type 2 (PCV2), both gE and gD genes of pseudorabies virus (PRV) and porcine parvovirus (PPV), the LAMP assay showed a high specific detection of PCV3. A visible detection method was developed using SYBR Green I to recognize the results rapidly. Based on the detection of 20 clinical tissue samples, the LAMP assay was more practical and convenient than classical PCR due to its simplicity, high sensitivity, rapidity, specificity, visibility and cost efficiency.

Presence of Torque teno sus virus 1 and 2 in porcine circovirus 3-positive pigs

In this study, the co-infection of Torque teno sus virus (TTSuV) and porcine circovirus type 3 (PCV3) was reported. One hundred and ten of 132 (83.3%) PCV3-positive samples were co-infected with Torque teno sus virus 1 (TTSuV1). Ninety-four of 132 (71.2%) PCV3-positive samples were co-infected with Torque teno sus virus 2 (TTSuV2). Sixty-six of 132 (50.0%) of PCV3-positive samples were co-infected with both TTSuV1 and TTSuV2. There were no clinical signs of infection in pigs that were both PCV3-positive and PCV2-negative, in either multiparous sows or live-born infants. The high co-infection rate provides valuable information for the further study of the pathological correlation between PCV3 and TTSuVs.

The occurrence of porcine circovirus 3 without clinical infection signs in Shandong Province

Porcine circovirus type 3 (PCV3) was detected in Shandong, China. One hundred and thirty‐two of 222 (59.46%) samples were PCV3 positive, while 52 of 132 (39.39%) samples were co‐infected with PCV2. There were no clinical signs of infection in either multiparous sows or live‐born infants. Two strains of PCV3 were indentified from natural stillborn foetuses. Phylogenetic analysis showed the two strains of PCV3 are 96% identical to the known PCV3/Pig/USA (KX778720.1, KX966193.1 and KX898030.1) and closely related to Barbel Circovirus. Further studies of the epidemiology of PCV3 and the co‐infection with PCV2 are needed.

Withaferin A attenuates lipopolysaccharide-induced acute lung injury in neonatal rats

Withaferin A (WFA) is an active compound from Withania somnifera and has been reported to exhibit a variety of pharmacological activities such as anti&mdash;inflammatory, immunomodulatory and anti&mdash;tumor properties. In the present study, we investigated the potential protective role of WFA on acute lung injury in neonatal rats induced by lipopolysaccharide (LPS). We found that WFA significantly attenuated the pathological changes of lungs induced by LPS injection. Administration with WFA obviously decreased pulmonary neutrophil infiltration accompanied with decreased MPO concentrations. WFA also reduced the expression of pro&mdash;inflammatory cytokines including MIP&mdash;2, TNF&mdash;&#945;, IL&mdash;1&#946; and IL&mdash;6. Meanwhile, the expression levels of anti&mdash;inflammatory mediators such as TGF&mdash;&#946;1 and IL&mdash;10 were significantly increased following WFA administration. Moreover, WFA protected LPS&mdash;treated rats from oxidative damage via up&mdash;regulation of TBARS and H2O2 concentrations and down&mdash;regulation of ROS contents. Taken together, the present study demonstrated that WFA administration attenuated LPS&mdash;induced lung injury through inhibition of inflammatory responses and oxidative stress.

Retinal and choroidal thickness evaluation by SD-OCT in adults with obstructive sleep apnea-hypopnea syndrome (OSAS)

OBJECTIVE

To assess the macular retina and choroidal thickness change in patients with obstructive sleep apnea-hypopnea syndrome (OSAS) with no significant symptoms and pathological changes in the fundus using spectral domain-optical coherence tomography.

METHODS

This prospective, observational case-control study consisted of 53 eyes of 53 patients with OSAS and 12 eyes of 12 age-matched controls. Macular and choroidal thicknesses were measured by optical coherence tomography.

RESULTS

The foveal and nasal macular thicknesses were significantly different between four groups (P=0.001, P=0.016). The foveal thickness of the control group was significantly thinner than that of the severe group (P=0.000). The nasal macular thickness of the control group was significantly thinner than that of the severe group (P=0.008). A significant correlation was found between oxygen desaturation index (ODI) and macular center thickness (r=0.357, R(2)=0.127, P=0.004), with an ODI coefficient of 0.457 (P=0.004). Similarly, a significant correlation was found between ODI and nasal macular thickness (r=0.265, R(2)=0.070, P=0.033), with an ODI coefficient of 0.233 (P=0.033). The subfoveal choroidal thickness was significantly different among the groups (F=3.657, P=0.017). The subfoveal choroidal thickness of the severe group was significantly thinner than that of the control group, mild group, and moderate group (P=0.023, 0.006, and 0.036, respectively). The choroidal thickness 1 mm nasal to the fovea was significantly different between the groups after correcting for age and diopter (F=3.411, P=0.023). The choroidal thickness 1 mm nasal to the fovea was significantly thinner in the severe group compared with the control group and mild group (P=0.013 and 0.010, respectively). Choroidal thickness was significantly correlated with diopter (r=0.520, R(2)=0.270, P<0.001), with a coefficient of 0.327 (P<0.001), and with ODI (r=0.520, R(2)=0.165, P=0.001), with a coefficient of -0.370 (P=0.001).

CONCLUSIONS

OSAS patients showed decreased foveal and nasal macular thickness, similar to the subfoveal and nasal choroidal thickness. These findings suggest that, because of intermittent hypoxia, OSAS might change the retinal and choroidal blood supply.

Efficient inhibition of B-cell lymphoma xenografts with a novel recombinant fusion protein: anti-CD20Fab-LDM

Lidamycin (LDM) is a new member of enediyne antitumor antibiotics family that can be separated and reconstituted. It consists of a labile active enediyne chromophore (AE) and a noncovalently bound apoprotein (LDP). LDM is now in phase II clinical trials. In this study, we described the antitumor features of a fusion protein of LDM, anti-CD20Fab-LDM, targeted to CD20 expressed by B-lymphoid malignancies. Especially, LDM was prepared by a novel two-step method including DNA recombination and molecular reconstitution. Anti-CD20Fab-LDM exerted potent cytotoxicity against CD20+ B-cell lymphoma cell lines in vitro (IC50: 10-30 pM) and in the Raji xenograft model. Two Raji xenografts were allowed to grow to an initial mass of 80 and 500 mm³, respectively, and then anti-CD20Fab-LDM was administered intravenously with the highest dose of 4 nmol kg⁻¹ . The inhibition rates of tumor growth were 90.1 and 85%, which were saliently superior to those of nontargeted LDM. It is noteworthy that anti-CD20Fab-LDM can inhibit the growth of patient-derived cells, including rituximab-resistant patient-derived cells. Thus, CD20-targeted delivery of LDM is a specific and potent therapeutic strategy for B-lymphoid malignancies. In addition, the two-step approach could serve as a new technology platform for making a series of highly potent engineered antibody-based drugs.

FTY720 suppresses interleukin-1beta-induced secretory phospholipase A2 expression in renal mesangial cells by a transcriptional mechanism

BACKGROUND AND PURPOSE

FTY720 is a potent immunomodulatory prodrug that is converted to its active phosphorylated form by a sphingosine kinase. Here we have studied whether FTY720 mimicked the action of sphingosine-1-phosphate (S1P) and exerted an anti-inflammatory potential in renal mesangial cells.

EXPERIMENTAL APPROACH

Prostaglandin E(2) (PGE(2)) was quantified by an enzyme-linked immunosorbent-assay. Secretory phospholipase A(2) (sPLA(2)) protein was detected by Western blot analyses. mRNA expression was determined by Northern blot analysis and sPLA(2)-promoter activity was measured by a luciferase-reporter-gene assay.

KEY RESULTS

Stimulation of cells for 24 h with interleukin-1beta (IL-1beta) is known to trigger increased PGE(2) formation which coincides with an induction of the mRNA for group-IIA-sPLA(2) and protein expression. FTY720 dose-dependently suppressed IL-1beta-induced IIA-sPLA(2) protein secretion and activity in the supernatant. This effect is due to a suppression of cytokine-induced sPLA(2) mRNA expression which results from a reduced promoter activity. As a consequence of suppressed sPLA(2) activity, PGE(2) formation is also reduced by FTY720. Mechanistically, the FTY720-suppressed sPLA(2) expression results from an activation of the TGFbeta/Smad signalling cascade since inhibition of the TGFbeta receptor type I by a specific kinase inhibitor reverses the FTY720-mediated decrease of sPLA(2) protein expression and sPLA(2) promoter activity.

CONCLUSIONS AND IMPLICATIONS

In summary, our data show that FTY720 was able to mimic the anti-inflammatory activity of TGFbeta and blocked cytokine-triggered sPLA(2) expression and subsequent PGE(2) formation. Thus, FTY720 may exert additional in vivo effects besides the well reported immunomodulation and its anti-inflammatory potential should be considered.

The Biomolecular Interaction Network Database and related tools 2005 update

The Biomolecular Interaction Network Database (BIND) (http://bind.ca) archives biomolecular interaction, reaction, complex and pathway information. Our aim is to curate the details about molecular interactions that arise from published experimental research and to provide this information, as well as tools to enable data analysis, freely to researchers worldwide. BIND data are curated into a comprehensive machine-readable archive of computable information and provides users with methods to discover interactions and molecular mechanisms. BIND has worked to develop new methods for visualization that amplify the underlying annotation of genes and proteins to facilitate the study of molecular interaction networks. BIND has maintained an open database policy since its inception in 1999. Data growth has proceeded at a tremendous rate, approaching over 100 000 records. New services provided include a new BIND Query and Submission interface, a Standard Object Access Protocol service and the Small Molecule Interaction Database (http://smid.blueprint.org) that allows users to determine probable small molecule binding sites of new sequences and examine conserved binding residues.

Sequence of HA gene of avian influenza A/Chicken/Guangdong/SS/1994 (H9N2) virus

The RNA of the hemagglutinin (HA) gene of A/Chicken/Guangdong/SS/1994 (H9N2) was reverse transcription-polymerase chain reaction amplified, and the cDNA was cloned into a plasmid vector. The complete coding sequence of the HA gene was sequenced and included 1683 nucleotides, which encoded for a protein of 560 amino acids. The potential glycosylation sites related to HA protein function were highly conserved. The amino acid sequence of the HA proteolytic cleavage was G-S-S-R/G. This cleavage site sequence is compatible with a low-pathogenic avian influenza virus. Sequence comparison of this HA gene with other H9 influenza virus sequences in the GenBank database showed a 82%-97% nucleotide and amino acid sequence similarity.

Cysteine-3635 is responsible for skeletal muscle ryanodine receptor modulation by NO

We have shown previously that at physiologically relevant oxygen tension (pO(2) approximately 10 mmHg), NO S-nitrosylates 1 of approximately 50 free cysteines per ryanodine receptor 1 (RyR1) subunit and transduces a calcium-sensitizing effect on the channel by means of calmodulin (CaM). It has been suggested that cysteine-3635 is part of a CaM-binding domain, and its reactivity is attenuated by CaM [Porter Moore, C., Zhang, J. Z., Hamilton, S. L. (1999) J. Biol. Chem. 274, 36831-36834]. Therefore, we tested the hypothesis that the effect of NO was mediated by C3635. The full-length RyR1 single-site C3635A mutant was generated and expressed in HEK293 cells. The mutation resulted in the loss of CaM-dependent NO modulation of channel activity and reduced S-nitrosylation by NO to background levels but did not affect NO-independent channel modulation by CaM or the redox sensitivity of the channel to O(2) and glutathione. Our results reveal that different cysteines within the channel have been adapted to serve in nitrosative and oxidative responses, and that S-nitrosylation of the cysteine-containing CaM-binding domain underlies the mechanism of CaM-dependent regulation of RyR1 by NO.

Identification and functional characterization of a novel ryanodine receptor mutation causing malignant hyperthermia in North American and South American families

Malignant hyperthermia is a pharmacogenetic disorder associated with mutations in Ca(2+) regulatory proteins. It manifests as a hypermetabolic crisis triggered by commonly used anesthetics. Malignant hyperthermia susceptibility is a dominantly inherited predisposition to malignant hyperthermia that can be diagnosed by using caffeine/halothane contracture tests. In a multigenerational North American family with a severe form of malignant hyperthermia that has caused four deaths, a novel RYR1 A2350T missense mutation was identified in all individuals testing positive for malignant hyperthermia susceptibility. The same A2350T mutation was identified in an Argentinean family with two known fatal MH reactions. Functional analysis in HEK-293 cells revealed an altered Ca(2+) dependence and increased caffeine sensitivity of the expressed mutant protein thus confirming the pathogenic potential of the RYR1 A2350T mutation.

Identification of apocalmodulin and Ca2+-calmodulin regulatory domain in skeletal muscle Ca2+ release channel, ryanodine receptor

Fusion proteins and full-length mutants were generated to identify the Ca(2+)-free (apoCaM) and Ca(2+)-bound (CaCaM) calmodulin binding sites of the skeletal muscle Ca(2+) release channel/ryanodine receptor (RyR1). [(35)S]Calmodulin (CaM) overlays of fusion proteins revealed one potential Ca(2+)-dependent (aa 3553-3662) and one Ca(2+)-independent (aa 4302-4430) CaM binding domain. W3620A or L3624D substitutions almost abolished completely, whereas V3619A or L3624A substitutions reduced [(35)S]CaM binding to fusion protein (aa 3553-3662). Three full-length RyR1 single-site mutants (V3619A,W3620A,L3624D) and one deletion mutant (Delta4274-4535) were generated and expressed in human embryonic kidney 293 cells. L3624D exhibited greatly reduced [(35)S]CaM binding affinity as indicated by a lack of noticeable binding of apoCaM and CaCaM (nanomolar) and the requirement of CaCaM (micromolar) for the inhibition of RyR1 activity. W3620A bound CaM (nanomolar) only in the absence of Ca(2+) and did not show inhibition of RyR1 activity by 3 microm CaCaM. V3619A and the deletion mutant bound apoCaM and CaCaM at levels compared with wild type. V3619A activity was inhibited by CaM with IC(50) approximately 200 nm, as compared with IC(50) approximately 50 nm for wild type and the deletion mutant. [(35)S]CaM binding experiments with sarcoplasmic reticulum vesicles suggested that apoCaM and CaCaM bind to the same region of the native RyR1 channel complex. These results indicate that the intact RyR1 has a single CaM binding domain that is shared by apoCaM and CaCaM.

Evidence for a role of the lumenal M3-M4 loop in skeletal muscle Ca(2+) release channel (ryanodine receptor) activity and conductance

We tested the hypothesis that part of the lumenal amino acid segment between the two most C-terminal membrane segments of the skeletal muscle ryanodine receptor (RyR1) is important for channel activity and conductance. Eleven mutants were generated and expressed in HEK293 cells focusing on amino acid residue I4897 homologous to the selectivity filter of K(+) channels and six other residues in the M3-M4 lumenal loop. Mutations of amino acids not absolutely conserved in RyRs and IP(3)Rs (D4903A and D4907A) showed cellular Ca(2+) release in response to caffeine, Ca(2+)-dependent [(3)H]ryanodine binding, and single-channel K(+) and Ca(2+) conductances not significantly different from wild-type RyR1. Mutants with an I4897 to A, L, or V or D4917 to A substitution showed a decreased single-channel conductance, loss of high-affinity [(3)H]ryanodine binding and regulation by Ca(2+), and an altered caffeine-induced Ca(2+) release in intact cells. Mutant channels with amino acid residue substitutions that are identical in the RyR and IP(3)R families (D4899A, D4899R, and R4913E) exhibited a decreased K(+) conductance and showed a loss of high-affinity [(3)H]ryanodine binding and loss of single-channel pharmacology but maintained their response to caffeine in a cellular assay. Two mutations (G4894A and D4899N) were able to maintain pharmacological regulation both in intact cells and in vitro but had lower single-channel K(+) and Ca(2+) conductances than the wild-type channel. The results support the hypothesis that amino acid residues in the lumenal loop region between the two most C-terminal membrane segments constitute a part of the ion-conducting pore of RyR1.

Evidence for a role of C-terminus in Ca(2+) inactivation of skeletal muscle Ca(2+) release channel (ryanodine receptor)

Six chimeras of the skeletal muscle (RyR1) and cardiac muscle (RyR2) Ca(2+) release channels (ryanodine receptors) previously used to identify RyR1 dihydropyridine receptor interactions [Nakai et al. (1998) J. Biol. Chem. 273, 13403] were expressed in HEK293 cells to assess their Ca(2+) dependence in [(3)H]ryanodine binding and single channel measurements. The results indicate that the C-terminal one-fourth has a major role in Ca(2+) activation and inactivation of RyR1. Further, our results show that replacement of RyR1 regions with corresponding RyR2 regions can result in loss and/or reduction of [(3)H]ryanodine binding affinity while maintaining channel activity.

Protein loss from axonal transport occurs without diminution of vesicle traffic

Protein loss from the rapid anterograde axonal transport system of amphibian sensory nerve fibers was compared with the numbers and sizes of anterogradely transported vesicles in the axons. Protein was found to be lost at a rate of approximately 2% per millimeter of nerve traversed. However, no changes were observed in either the numbers or sizes of vesicles in the nerve at two locations separated by 60-75 mm. The results show that protein loss is not explained as a loss of vesicles from the transport system nor by a reduction in vesicle size.