Hibernation Induces Expression of Moesin in Intestinal Epithelial Cells

Abstract

Identification of proteins that are differentially expressed in mammals that hibernate can provide insight into mechanisms that preserve cellular function at low temperatures. A candidate protein was identified in intestinal brush border membranes of 13-lined ground squirrels. Intestinal brush border membrane proteins were separated using SDS–PAGE and gels were stained with Coomassie blue. We observed a ∼75-kDa band that was specifically increased in brush border membranes isolated from torpid squirrels compared with summer active squirrels. The 75-kDa band was cut from one-dimensional gels and sequenced. A 17 amino acid sequence was identified of which amino acids 2–17 matched exactly a portion of moesin, a membrane–cytoskeletal linking protein and member of the ERM (ezrin/radixin/moesin) family. The sequence results were confirmed using anti-moesin antibodies that detected strong bands at ∼75 kDa on Western blots of brush border membranes in torpid squirrels (Tb∼7°C) and only faint signals in summer squirrels (Tb∼37°C) or aroused hibernators (Tb∼37°C). In contrast, signals obtained using anti-ezrin antibodies were uniformly strong in all squirrels, regardless of activity state. Intestinal brush borders of mice and rats expressed ezrin but not moesin. These results provide evidence for the physiological induction of an ERM protein in intestinal epithelial cells of torpid hibernators and support the idea that hibernation involves differential expression of gene products that may facilitate viability of cells at low temperatures.