Mitochondrial oxidative phosphorylation and energetic status are reflected by morphology of mitochondrial network in INS-1E and HEP-G2 cells viewed by 4Pi microscopy

• Published in: Biochimica et biophysica acta Vol. 1777; no. 7-8; pp. 834 - 846
• Main Authors: Plecitá-Hlavatá, Lydie, Lessard, Mark, Šantorová, Jitka, Bewersdorf, Joerg, Ježek, Petr
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2008
• Subjects: 3D morphology of mitochondrial network; 4Pi microscopy; Animals; Carcinoma, Hepatocellular; Cell Line, Tumor; Energy Metabolism; Hepatocellular carcinoma HEP-G2 cell; Humans; Image Processing, Computer-Assisted; Insulinoma; Insulinoma INS-1E cell; Liver Neoplasms; Microscopy, Confocal; Mitochondria - metabolism; Mitochondria - pathology; Mitochondria - ultrastructure; Oxidative Phosphorylation; Pancreatic Neoplasms; Rats; Uncoupling; mRoGFP; 3D morphology of mitochondrial network; Uncoupling; Hepatocellular carcinoma HEP-G2 cell; Oxidative phosphorylation; Insulinoma INS-1E cell; 4Pi microscopy; FCCP
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2008.04.002

Mitochondria in numerous cell types, especially in cultured cells, form a reticular network undergoing constant fusion and fission. The three dimensional (3D) morphology of these networks however has not been studied in detail to our knowledge. We have investigated insulinoma INS-1E and hepatocellular carcinoma HEP-G2 cells transfected with mitochondria-addressed GFP. Using 4Pi microscopy, 3D morphology changes responding to decreased oxidative phosphorylation and/or energetic status could be observed in these cells at an unprecedented 100 nm level of detail. In INS-1E cells cultivated at 11 mM glucose, the mitoreticulum appears predominantly as one interconnected mitochondrion with a nearly constant 262±26 nm tubule diameter. If cultured at 5 mM glucose, INS-1E cells show 311±36 nm tubules coexisting with numerous flat cisternae. Similar interconnected 284±38 nm and 417±110 nm tubules were found in HEP-G2 cells cultivated at 5 mM and hyperglycaemic 25 mM glucose, respectively. With rotenone inhibiting respiration to ~10%, disintegration into several reticula and numerous ~300 nm spheres or short tubules was observed. De-energization by uncoupling additionally led to formation of rings and bulky cisternae of 1.4±0.4 μm diameter. Rotenone and uncoupler acted synergically in INS-1E cells and increased fusion (ongoing with fission) forming bowl-like shapes. In HEP-G2 cells fission partially ceased with FCCP plus rotenone. Thus we have revealed previously undescribed details for shapes upon mitochondrial disintegration and clearly demonstrate that high resolution 3D microscopy is required for visualization of mitochondrial network. We recommend 4Pi microscopy as a new standard.