Alternative splicing isoform in succinate dehydrogenase complex, subunit C causes downregulation of succinate-coenzyme Q oxidoreductase activity in mitochondria

Abstract

Mitochondrial succinate dehydrogenase (SDH) is localized to the inner mitochondrial membrane and is responsible for the redox of succinic acid. SDH is a tetrameric iron-sulfur flavoprotein of the tricarboxylic acid cycle and respiratory chain. The SDH complex, subunit C (SDHC) transcript has deletion-type alternative splicing sites. Generally, alternative splicing produces variant proteins and expression patterns, as products of different genes. In certain cases, specific alternative splicing variants (ASVs) have been associated with human disease. Due to a frameshift mutation causing loss of the heme binding region, the SDHC Δ5 isoform (lacking exon 5) exhibits no SDHC activity. To investigate whether the SDHC splicing variants can function as dominant-negative inhibitors, SDHC ASVs were overexpressed in HCT-15 human colorectal cancer cells. Using real-time reverse transcription-polymerase chain reaction, a dominant-negative effect of the Δ5 isoform on SDHC mRNA was shown. In addition, Δ5 overexpression increased the levels of reactive oxygen species. Furthermore, in the Δ5 isoform-overexpressing cells, SDH activity was reduced. SDHC activation is a significant event during the electron transport chain, and the function of the SDHC Δ5 variant may be significant for the differentiation of tumor cells.

Differential susceptibility of mitochondrial complex II to inhibition by oxaloacetate in brain and heart

“…Due to the reported tissue specific heterogeneity of SDH [39] , [40] , [41] , we compared the sensitivity of the enzyme to OAA in heart and brain. Titration of succinate:Q 1 reductase activity by OAA using mitochondrial membranes from brain and heart showed similar affinity of the inhibitor to the enzyme in both tissues ( Fig.…”

“…Two tissue-specific isoforms of the large subunit SDHA, bearing succinate-binding site, have been identified [39] , [41] . In addition, SDHC transcript is subject to alternative splicing, resulting in three different isoforms, affecting enzyme activity [41] . Potentially, tissue-specific SDH isoforms could have different sensitivity to inhibitors and therefore we examined the effect of OAA on enzyme from brain and heart membranes.…”

WITHDRAWN: Effects of cancer-associated point mutations on the structure, function, and stability of succinate dehydrogenase A

“…SDH has recently been identified as a tumor suppressor gene (13,14). Consistent with the two-hit hypothesis, SDH mutations are often associated with the loss of normal alleles, resulting in the inactivation of SDH, which increases succinate and reactive oxygen species (ROS) levels and ultimately triggers tumor formation (11,12).…”

Inflammation-Induced Alternative Pre-mRNA Splicing in Mouse Alveolar Macrophages

“…Additionally, some genes that encode positive effectors of inflammatory signaling can also produce alternate pre-mRNA splice forms that encode negative regulators of signaling (Blumhagen et al 2017;De Arras and Alper 2013;Deng et al 2008;Gray et al 2010;Hardy and O'Neill 2004;Iwami et al 2000;Janssens et al 2002;Koop et al 2011;Palsson-McDermott et al 2009;Rao et al 2005;Rosenstiel et al 2006), thus mediating a negative feedback loop to limit the extent of the inflammatory response. In a similar fashion, alternative pre-mRNA splicing has been shown to alter cellular metabolism (Clower et al 2010;Yang and Lu 2013;Satoh et al 2015). While inflammation-induced alternative pre-mRNA splicing in macrophages has been investigated on a genome-wide scale in vitro (Beyer et al 2012;Bhatt et al 2012;Lin et al 2016;O'Connor et al 2015;Pai et al 2016;Pandya-Jones et al 2013), to our knowledge it has not been investigated in vivo.…”