Effects of anoxic exposure on the nuclear factor of activated T cell (NFAT) transcription factors in the stress ‐tolerant wood frog

The wood frog,Lithobates sylvaticus (also known asRana sylvatica), is used for studying natural freeze tolerance. These animals convert 65% to 70% of their total body water into extracellular ice and survive freezing for weeks in winter. Freezing interrupts oxygen delivery to organs; thus, wood frogs limit their ATP usage by depressing their metabolism and redirecting the available energy only to prosurvival processes. Here, we studied the nuclear factor of activated T cell (NFAT) transcription factor family in response to 24 ‐hour anoxia, and 4‐hour aerobic recovery in liver and skeletal muscle. Protein expression levels of NFATc1‐c4, calcineurin A and glycogen synthase kinase 3β (NFAT regulators), osteopontin, and atrial natriuretic peptide (ANP) (targets of NFATc3 and NFATc4, respectively) were measured by immu noblotting, and the DNA‐binding activities of NFATc1‐c4 were measured by DNA‐protein interaction ELISAs. Results show that NFATc4, calcineurin, and ANP protein expression as well as NFATc4 DNA binding increased during anoxia in liver where calcineurin and ANP protein levels and NFATc4 DNA bind ing remaining high after aerobic recovery. Anoxia caused a significant increase in NFATc3 protein expression but not DNA‐binding activity in muscle. Our results show that anoxia can increase NFATc4 transcriptional activity in liver, leading to the increase in expression of cytoprotective genes in the wood frog. Understanding the molecular mechanisms involved in ...
Source: Cell Biochemistry and Function - Category: Biochemistry Authors: Tags: RESEARCH ARTICLE Source Type: research