Molecular Medicine Molecular Identification and Functional Characterization of a Mitochondrial Sulfonylurea Receptor 2 Splice Variant Generated by Intraexonic Splicing
نویسندگان
چکیده
Rationale: Cardioprotective pathways may involve a mitochondrial ATP-sensitive potassium (mitoKATP) channel but its composition is not fully understood. Objective: We hypothesized that the mitoKATP channel contains a sulfonylurea receptor (SUR)2 regulatory subunit and aimed to identify the molecular structure. Methods and Results: Western blot analysis in cardiac mitochondria detected a 55-kDa mitochondrial SUR2 (mitoSUR2) short form, 2 additional short forms (28 and 68 kDa), and a 130-kDa long form. RACE (Rapid Amplification of cDNA Ends) identified a 1.5-Kb transcript, which was generated by a nonconventional intraexonic splicing (IES) event within the 4th and 29th exons of the SUR2 mRNA. The translated product matched the predicted size of the 55-kDa short form. In a knockout mouse (SUR2KO), in which the SUR2 gene was disrupted, the 130-kDa mitoSUR2 was absent, but the short forms remained expressed. Diazoxide failed to induce increased fluorescence of flavoprotein oxidation in SUR2KO cells, indicating that the diazoxide-sensitive mitoKATP channel activity was associated with 130-kDa–based channels. However, SUR2KO mice displayed similar infarct sizes to preconditioned wild type, suggesting a protective role for the remaining short form-based channels. Heterologous coexpression of the SUR2 IES variant and Kir6.2 in a K transport mutant Escherichia coli strain permitted improved cell growth under acidic pH conditions. The SUR2 IES variant was localized to mitochondria, and removal of a predicted mitochondrial targeting sequence allowed surface expression and detection of an ATP-sensitive current when coexpressed with Kir6.2. Conclusions: We identify a novel SUR2 IES variant in cardiac mitochondria and provide evidence that the variant-based channel can form an ATP-sensitive conductance and may contribute to cardioprotection. (Circ Res. 2009;105:1083-1093.)
منابع مشابه
Molecular identification and functional characterization of a mitochondrial sulfonylurea receptor 2 splice variant generated by intraexonic splicing.
RATIONALE Cardioprotective pathways may involve a mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel but its composition is not fully understood. OBJECTIVE We hypothesized that the mitoK(ATP) channel contains a sulfonylurea receptor (SUR)2 regulatory subunit and aimed to identify the molecular structure. METHODS AND RESULTS Western blot analysis in cardiac mitochondria detected a 55...
متن کاملIdentification of a Novel Splice Site Mutation in RUNX2 Gene in a Family with Rare Autosomal Dominant Cleidocranial Dysplasia
Introduction: Pathogenic variants of RUNX2, a gene that encodes an osteoblast-specific transcription factor, have been shown as the cause of CCD, which is a rare hereditary skeletal and dental disorder with dominant mode of inheritance and a broad range of clinical variability. Due to the relative lack of clinical complications resulting in CCD, the medical diagnosis of this disorder is challen...
متن کاملIdentification of Spata-19 New Variant with Expression beyond Meiotic Phase of Mouse Testis Development
Background: The study of specific genes expressed in the testis is important to understanding testis development and function. Spermatogenesis is an attractive model for the study of gene expression during germ cell differentiation. Spermatogenesis associated-19 (Spata-19) is a recently-identified important spermatogenesis-related gene specifically expressed in testis. Its protein product is in...
متن کاملFour novel splice variants of sulfonylurea receptor 1.
ATP-sensitive K(+) (K(ATP)) channels are composed of pore-forming Kir6.x subunits and regulatory sulfonylurea receptor (SUR) subunits. SURs are ATP-binding cassette proteins with two nucleotide-binding folds (NBFs) and binding sites for sulfonylureas, like glibenclamide, and for channel openers. Here we report the identification and functional characterization of four novel splice forms of guin...
متن کاملExpression profile of ZFX isoform3/variant 5 in gastric cancer tissues and its association with tumor size
Objective(s):Previous studies demonstrate that changes in pre-mRNA splicing play a significant role in human disease development. Furthermore, many cancer-associated genes are regulated by alternative splicing. There are mounting evidences that splice variants which express predominantly in tumors, have clear diagnostic value and may provide potential drug targets. Located on the X chromosome, ...
متن کامل