Right-to-left ventricular differences in the expression of mitochondrial hexokinase and phosphorylation of Akt.
OBJECTIVE
Hexokinase (HK) is a key glycolytic enzyme which promotes the maintenance of glucose homeostasis in cardiomyocytes. HK1 isoform is predominantly bound to the outer mitochondrial membrane and highly supports oxidative phosphorylation by increasing the availability of ADP for complex V of the respiratory chain. HK2 isoform is under physiological conditions predominantly localized in the cytosol and upon stimulation of PI3K/ Akt pathway associates with mitochondria and thus can prevent apoptosis. The purpose of this study was to investigate expression and subcellular localization of both HK isoforms in left (LV) and right (RV) heart ventricles of adult male Wistar rats.


METHODS
Real-Time RT-PCR, Western blotting, and quantitative immunofluorescence microscopy were used.


RESULTS
Our results showed a significantly higher expression of both HK1 and HK2 at mRNA and protein levels in the RV compared to the LV. These findings were corroborated by immunofluorescence staining which revealed substantially higher fluorescence signals of both HKs in the RV than in the LV. The ratios of phospho-Ser473-Akt/non-phospho-Akt and phospho-Thr308-Akt/non-phospho-Akt were also markedly higher in the RV than in the LV.


CONCLUSIONS
These results suggest that the RV has a higher activity of aerobic glycolytic metabolism and may be able to respond faster and more powerfully to stressful stimuli than the LV.
Department of Physiology, Faculty of Science, Charles University in Prague, Prague.
Petra
P
Waskova-Arnostova
Barbara
B
Elsnicova
Dita
D
Kasparova
Ondrej
O
Sebesta
Jiri
J
Novotny
Jan
J
Neckar
Frantisek
F
Kolar
Jitka
J
Zurmanova
D000818:Animals; D006352:Heart Ventricles / Q000378:metabolism*; D006593:Hexokinase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D007527:Isoenzymes; D012333:RNA, Messenger; D006593:Hexokinase; D051057:Proto-Oncogene Proteins c-akt