Abstract
Intracellular temperature affects a wide range of cellular functions in living organisms. However, it remains unclear whether temperature in individual animal cells is controlled autonomously as a response to fluctuations in environmental temperature. Using two distinct intracellular thermometers, we find that the intracellular temperature of steady-state Drosophila S2 cells is maintained in a manner dependent on Δ9-fatty acid desaturase DESAT1, which introduces a double bond at the Δ9 position of the acyl moiety of acyl-CoA. The DESAT1-mediated increase of intracellular temperature is caused by the enhancement of F1Fo-ATPase-dependent mitochondrial respiration, which is coupled with thermogenesis. We also reveal that F1Fo-ATPase-dependent mitochondrial respiration is potentiated by cold exposure through the remodeling of mitochondrial cristae structures via DESAT1-dependent unsaturation of mitochondrial phospholipid acyl chains. Based on these findings, we propose a cell-autonomous mechanism for intracellular temperature control during environmental temperature changes.
Highlights
As temperature is an important physicochemical parameter that governs biochemical reactions and biomolecular dynamics, intracellular temperature has the potential to influence a broad range of cellular functions (Okabe et al, 2018)
Production of unsaturated fatty acids by DESAT1 maintains the intracellular temperature of Drosophila S2 cells To investigate whether the unsaturated fatty acid biosynthesis pathway is involved in intracellular temperature control in Drosophila S2 cells, we established a Desat1-deficient cell line using the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system (Figures 1A and S1A) (Bassett et al, 2014)
The decrease in fluorescent polymeric thermometer (FPT) fluorescence lifetime in Desat1-deficient cells was rescued by monounsaturated fatty acid (C16:1 and C18:1) supplementation of the culture medium or exogenous expression of DESAT1-FLAG (Figure 1D), showing that Desat1 deletion causes the decrease in intracellular temperature
Summary
As temperature is an important physicochemical parameter that governs biochemical reactions and biomolecular dynamics, intracellular temperature has the potential to influence a broad range of cellular functions (Okabe et al, 2018). Since changes in the environmental temperature directly affect the intracellular temperature and biological functions of ectotherms, as well as the peripheral tissues in endotherms, the regulation of intracellular temperature during environmental temperature changes is essential for maintaining homeostasis in living cells. It remains unclear how individual animal cells autonomously regulate their intracellular temperature in response to environmental temperature changes
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