Presynaptic BK channel localization is dependent on the hierarchical organization of alpha-catulin and dystrobrevin and fine-tuned by CaV2 calcium channels

BACKGROUND: Large conductance, calcium-activated BK channels regulate many important physiological processes, including smooth muscle excitation, hormone release and synaptic transmission. The biological roles of these channels hinge on their unique ability to respond synergistically to both voltage and cytosolic calcium elevations. Because calcium influx is meticulously regulated both spatially and temporally, the localization of BK channels near calcium channels is critical for their proper function. However, the mechanism underlying BK channel localization near calcium channels is not fully understood. RESULTS: We show here that in C. elegans the localization of SLO-1/BK channels to presynaptic terminals, where UNC-2/CaV2 calcium channels regulate neurotransmitter release, is controlled by the hierarchical organization of CTN-1/alpha-catulin and DYB-1/dystrobrevin, two proteins that interact with cortical cytoskeletal proteins. CTN-1 organizes a macromolecular SLO-1 channel complex at presynaptic terminals by direct physical interaction. DYB-1 contributes to the maintenance or stabilization of the complex at presynaptic terminals by interacting with CTN-1. We also show that SLO-1 channels are functionally coupled with UNC-2 calcium channels, and that normal localization of SLO-1 to presynaptic terminals requires UNC-2. In the absence of UNC-2, SLO-1 clusters lose the localization specificity, thus accumulating inside and outside of presynaptic terminals. Moreover, CTN-1 is also similarly localized in unc-2 mutants, consistent with the direct interaction between CTN-1 and SLO-1. However, localization of UNC-2 at the presynaptic terminals is not dependent on either CTN-1 or SLO-1. Taken together, our data strongly suggest that the absence of UNC-2 indirectly influences SLO-1 localization via the reorganization of cytoskeletal proteins. CONCLUSION: CTN-1 and DYB-1, which interact with cortical cytoskeletal proteins, are required for the presynaptic punctate localization of SLO-1 in a hierarchical manner. In addition, UNC-2 calcium channels indirectly control the fidelity of SLO-1 puncta localization at presynaptic terminals. We suggest that the absence of UNC-2 leads to the reorganization of the cytoskeletal structure that includes CTN-1, which in turn influences SLO-1 puncta localization

Head and Neck Lymphomas: Tip of the Iceberg?

ABSTRACT Background: Lymphomas comprise around 5% of all head and neck neoplasms and is the second most common extra nodal non hodgkin's lymphoma (NHL). However there is sporadic data on this entity from the subcontinent and hence we undertook this study. Methodology: This retrospective observational study was conducted at a tertiary care oncology center in India on diagnosed cases of NHL between January 2007 and December 2013. All patients were diagnosed based on histopathology and immunohistochemistry. Staging work up was done in all patients. Patients were considered as primary Head and Neck lymphomas if there was head and neck as the predominant site with or without regional lymph node involvement. Results: A total of 39 patients were studied. The age at presentation ranged from 29 to 78 years. The most common site of presentation was oral cavity (26%; n=10), followed by parotid and thyroid (18% each; n=7), eye (12%, n=5), maxilla (8%; n=3), paranasal sinuses (8%; n-=3) cheek (8%, n=3), and nasal cavity (2%, n=1). 41% (n=16) cases were in stage I, 43% (n=17) in stage II, 3% (n=1) in stage III, and 13% (n=5) were in stage IV. Most common histology was DLBCL (71%; n=28), followed by plasmablastic (10%; n=4), marginal zone (8%, n=3), mantle cell (3%; n=1), follicular lymphomas (5%; n=2), and NK/T cell lymphoma (3%; n=1). Most of the patients were of low risk (67%; n=26), followed by intermediate (23%; n=9), and high risk (10%; n=4). Patients were treated with anthracycline based chemotherapy +/-radiotherapy. In this study, stage I and stage II patients had a better prognosis and overall survival, median OS 28 months and 11 months, respectively. In stage III and IV, it was 7 and 3 months, respectively. According to site, the best median overall survival was seen with parotid (27 m), paranasal sinus (26m), and oral cavity (23 m), followed by thyroid (18 m) nasal cavity (17 m), maxilla (11 m), eye (8 m), and cheek (7 m)

An Alpha-Catulin Homologue Controls Neuromuscular Function through Localization of the Dystrophin Complex and BK Channels in Caenorhabditis elegans

The large conductance, voltage- and calcium-dependent potassium (BK) channel serves as a major negative feedback regulator of calcium-mediated physiological processes and has been implicated in muscle dysfunction and neurological disorders. In addition to membrane depolarization, activation of the BK channel requires a rise in cytosolic calcium. Localization of the BK channel near calcium channels is therefore critical for its function. In a genetic screen designed to isolate novel regulators of the Caenorhabditis elegans BK channel, SLO-1, we identified ctn-1, which encodes an α-catulin homologue with homology to the cytoskeletal proteins α-catenin and vinculin. ctn-1 mutants resemble slo-1 loss-of-function mutants, as well as mutants with a compromised dystrophin complex. We determined that CTN-1 uses two distinct mechanisms to localize SLO-1 in muscles and neurons. In muscles, CTN-1 utilizes the dystrophin complex to localize SLO-1 channels near L-type calcium channels. In neurons, CTN-1 is involved in localizing SLO-1 to a specific domain independent of the dystrophin complex. Our results demonstrate that CTN-1 ensures the localization of SLO-1 within calcium nanodomains, thereby playing a crucial role in muscles and neurons

Plasma Epstein Barr viral load in adult-onset Hodgkin lymphoma in South India

Objective/background: Epstein Barr Virus (EBV) DNA load is increasingly being used as a noninvasive biomarker for detecting EBV association in lymphomas. Since there is a need of data from India, we undertook to prospectively evaluate plasma EBV DNA load as a marker of EBV association in newly diagnosed adult-onset Hodgkin lymphoma (HL). Methods: EBV DNA was quantified using real-time polymerase chain reaction. In a subset of patients, an assay was validated qualitatively with EBV latent membrane protein-1 (LMP1) immunohistochemistry (IHC). Wherever possible, follow-up plasma samples post three cycles of chemotherapy were obtained. Results: Over a period of 10 months, 33 newly diagnosed adult-onset HL were enrolled in the study. Pretherapy plasma EBV DNA was detectable in ∼49% (16/33) patients (viral loads range, 1.0–51.2 × 103 copies/mL) and undetectable in 30 voluntary blood donors. LMP1 IHC was positive in 56% of cases tested (14/25). Sensitivity and specificity of plasma EBV DNA with respect to LMP1 IHC were 86% and 100%, respectively. Of the eight patients in whom follow-up plasma was available, in five EBV baseline-positive patients EBV load reverted to negative postchemotherapy and corroborated with clinical remission. Conclusion: Plasma EBV DNA load estimation may be useful in detecting EBV-association and possibly monitoring the response to therapy in EBV-related HL especially in our country where EBV association of HL is higher than in developed nations. Keywords: Epstein–Barr Virus, Hodgkin lymphoma, LMP1 immunohistochemistry, Real-time PCR, Viral loa

Interaction of α-catulin with dystrobrevin contributes to integrity of dystrophin complex in muscle

The dystrophin complex is a multimolecular membrane-associated protein complex whose defects underlie many forms of muscular dystrophy. The dystrophin complex is postulated to function as a structural element that stabilizes the cell membrane by linking the contractile apparatus to the extracellular matrix. Abetter understanding of how this complex is organized and localized will improve our knowledge of the pathogenic mechanisms of diseases that involve the dystrophin complex. In a Caenorhabditis elegans genetic study, we demonstrate that CTN-1/alpha-catulin, a cytoskeletal protein, physically interacts with DYB-1/alpha-dystrobrevin (a component of the dystrophin complex) and that this interaction is critical for the localization of the dystrophin complex near dense bodies, structures analogous to mammalian costameres. We further show that in mouse alpha-catulin is localized at the sarcolemma and neuromuscular junctions and interacts with alpha-dystrobrevin and that the level of alpha-catulin is reduced in alpha-dystrobrevin- deficient mouse muscle. Intriguingly, in the skeletal muscle of mdx mice lacking dystrophin, we discover that the expression of alpha-catulin is increased, suggesting a compensatory role of alpha-catulin in dystrophic muscle. Together, our study demonstrates that the interaction between alpha-catulin and alpha-dystrobrevin is evolutionarily conserved in C. elegans and mammalian muscles and strongly suggests that this interaction contributes to the integrity of the dystrophin complex

Primary gastrointestinal diffuse large B-cell lymphoma: A prospective study from South India

Background: Gastrointestinal tract (GIT) is the most common extranodal site for non-Hodgkin's lymphoma (NHL) and constitutes about 10%-15% of all NHL. This was a prospective study to evaluate the epidemiological, clinicopathological characteristics, and treatment outcome of primary GIT diffuse large B-cell lymphoma (PGIL). Materials and Methods: Newly diagnosed patients of PGIL with DLBCL histology were eligible. Lugano staging system was used. All patients were treated with prephase treatment (1 mg vincristine and 100 mg prednisolone) followed by CHOP-based chemotherapy (with or without rituximab) as definitive treatment. Results: A total of 21 patients of PGIL were diagnosed. The median age was 46 years (range: 27–69 years) with male:female ratio of 2:1. Dull aching abdominal pain was the most common presenting complaint. Stomach was the most common site involved (52.4%, n = 11) followed by the colon (23.8%, n = 5). The estimated median survival in patients with Stage IV disease was significantly lower as compared to patients with localized disease (Stage I and II) (6.23 months vs. 23.4 months; P = 0.04). Patients, who did not achieve complete response (CR), had 15.5 times higher risk of death, as compared to those who achieved CR (P = 0.01). Conclusions: Stomach was the most common site for PGIL. Localized disease and CR after first-line chemotherapy were associated with better survival. A higher cost of rituximab was the prohibitive factor for cure in these patients