Determination of the Subcellular Location of Spermidine Synthase, The

Grauberger, Kevin
The Stayton lab has performed a genome-wide survey of the early responses of the mouse heart transcriptome to acute myocardial infarction and reported a significant up-regulation in transcripts related to arginase metabolism. These transcripts included arginase 1 (ARG1), arginase 2 (ARG2), ornithine decarboxylase (ODC), antizyme inhibitor (AZI), spermidine synthase (SPDS), and spermidine-spermine N1-acetylase (SSAT). Two additional transcripts, spermine synthase (SPSY) and polyamine oxidase (PAO) did not show an up regulation in response to AMI. Our goal was to determine if the subcellular locations of SPDS, SSAT, PAO, and SPSY corresponded to the intercalated disc as J. Keele had shown for the initial enzymes ARG1, ODC, and AZI. Naïve mouse hearts were harvested, frozen in optical cutting temperature media, and cryosectioned. For these studies, we performed immunohistochemistry with antibodies to SPDS, SSAT, PAO, and SPSY, and known subcellular markers for the intercalated disc (n-cadherin), smooth muscle (calponin-3), and endothelial cells (MECA32). Our results show SPDS and SSAT to be localized with n-cadherin at the intercalated discs of cardiomyocytes. SPSY and PAO were found to be localized in the smooth muscle lining of the vasculature. Additionally, PAO appeared to be inter-nuclear and SSAT associated with the outer nuclear membrane.
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