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Pancreatic triacylglycerol lipase in a hibernating mammal. II. Cold-adapted function and differential expression

¹ Department of Biology, University of Minnesota Duluth, Duluth, Minnesota 55812
² Department of Genetics, North Carolina State University, Raleigh, North Carolina 27695-7614
³ Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110
⁴ Department of Biology, Francis Marion University, Florence, South Carolina 29501

Thirteen-lined ground squirrels (Spermophilus tridecemlineatus) exploit the low-temperature activity of pancreatic triacylglycerol lipase (PTL) during hibernation. Lipolytic activity at body temperatures associated with hibernation was examined using recombinant ground squirrel and human PTLs expressed in yeast. Both the human and ground squirrel enzymes displayed high activity at temperatures as low as 0°C and showed Q₁₀ values of 1.2–1.5 over a range of 37–7°C. These studies indicate that low-temperature lipolysis is a general property of PTL and does not require protein modifications unique to mammalian cells and/or the hibernating state. Western blots show elevated levels of PTL protein during hibernation in both heart and white adipose tissue (WAT). Significant increases in PTL gene expression are seen in heart, WAT, and testes; but not in pancreas, where PTL mRNA levels are highest. Upregulation of PTL in testes is also accompanied by expression of the PTL-specific cofactor, colipase. The multi-tissue expression of PTL during hibernation supports its role as a key enzyme that shows high activity at low temperatures.

lipolysis; low temperature; colipase; hibernation

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