Temperature-induced changes in the transbilayer distribution of phosphatidylethanolamine in mitoplasts of rainbow trout (Oncorhynchus mykiss) liver

Abstract

Increased proportions of phosphatidylethanolamine (PE) are a common adaptation of poikilothermic animals to life at cold temperatures. Although amino‐phospholipids such as PE are asymmetrically distributed between the two membrane hemilayers, the impact of temperature‐induced changes in phospholipid composition on PE asymmetry has not been examined. Accordingly, the distribution of PE between the inner and outer hemilayers of the inner membrane of liver mitochondria was determined in rainbow trout (Oncorhynchus mykiss) acclimated to 20°C and 5°C. Mitochondria were isolated from trout liver by a combination of differential and Nycodenz™ density‐gradient centrifugation, resulting in an 11‐ to 15‐fold enrichment in the activity of the mitochondrial enzyme marker succinate cytochrome c reductase. Interestingly, the outer mitochondrial membrane was more stable in 5°C‐ than 20°C‐acclimated trout as indicated by the higher concentration of digitonin (0.6 vs. 0.3 mg digitonin/mg mitochondrial protein) required for the preparation of mitoplasts. Phosphatidylethanolamines in the outer hemilayer of the inner mitochondrial membrane (IMM) were identified as derivatives of 2,4,6‐trinitrobenzene sulfonic acid (TNBS), a nonpenetrating reagent that reacts with primary amines. Our results demonstrate 1) a decrease in the phosphatidylcholine:phosphatidylethanolamine ratio in the IMM of 5°C‐ (1.43 ± 0.09) compared to 20°C‐ (2.31 ± 0.34) acclimated trout and 2) smaller amounts of PE in the outer hemilayer (6.0 ± 0.51%) of the IMM from 5°C‐ than 20°C‐acclimated trout (8.1 ± 0.55%). These results indicate that the composition of the inner mitochondrial membrane is enriched in PE at cold temperatures and that this enrichment is largely restricted to, and therefore most likely to be of functional significance to, the inner hemilayer. © 1996 Wiley‐Liss, Inc.

Changes in mitochondrial oxidative capacities during thermal acclimation of rainbow trout Oncorhynchus mykiss: roles of membrane proteins,phospholipids and their fatty acid compositions

“…higher activities of antioxidant enzymes), increases in PlsmPE in trout mitochondria during warm acclimation may compensate for thermally enhanced rates of lipid peroxidation reactions at warm temperatures. Interestingly, changes in the proportion of PE (no distinctions being made between plasmalogens and the corresponding diacyl) during thermal acclimation are largely restricted to the inner membrane of rainbow trout liver mitochondria (Miranda and Hazel, 1996). Such an asymmetrical distribution of PlsmPE in the inner membrane of mitochondria would facilitate that interaction with free radical species.…”

Oxygen limited thermal tolerance in fish?

“…As outlined above, a rise in aerobic capacity permits maintenance of cell functions in the cold (for review Guderley, 1998;Pörtner et al, , 2001. Associated processes are rising enzyme capacities (Crockett and Sidell, 1990;Guderley, 1990;Lannig et al, 2003), increased mitochondrial or capillary densities (Sisson and Sidell, 1987;Guderley and Blier, 1988;Ressel, 2001), changes in mitochondrial structure (Gaebel and Roots, 1989;St.-Pierre et al, 1998) and/or alterations in membrane composition (Miranda and Hazel, 1996;Logue et al, 2000). Mitochondrial densities are found esp.…”

Chilling Tolerance in Arabidopsis Involves ALA1, a Member of a New Family of Putative Aminophospholipid Translocases

“…Transbilayer redistribution of the aminophospholipid PE in response to cold has been reported before in poikilothermic animals (Miranda and Hazel, 1996). Several integral membrane enzyme activities, such as those of sarcoplasmic Ca 2ϩ -ATPase (Navarro et al, 1984) and the transduction enzyme protein kinase C (Stubb and Slater, 1996), are reported to be highly sensitive to the amount of bilayer-destabilizing lipid, such as PE, present in the membrane.…”

“…For example, an increased content of phosphatidylcholine (PC) in the outer leaflet and of anionic phospholipids in the inner leaflet has often been associated with distinct lipid fluidity of individual leaflets of biological membranes. Interestingly, in several poikilothermic organisms, asymmetric alterations in membrane phospholipid headgroup composition are associated with low-temperature adaptation (Hazel, 1995;Miranda and Hazel, 1996). In plants, asymmetric transbilayer distribution of phospholipids has been documented (Cheesebrough and Moore, 1980;Rawyler and Siegenthaler, 1981;Dorne et al, 1985;Tavernier and Pugin, 1995;O'Brien et al, 1997), but the physiological significance of the phenomenon is not known.…”