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Biochim Biophys Acta. 2015 Nov;1850(11):2196-202. doi: 10.1016/j.bbagen.2015.07.004. Epub 2015 Jul 17.

Post-translational regulation of PTEN catalytic function and protein stability in the hibernating 13-lined ground squirrel.

Author information

1
Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
2
Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. Electronic address: kenneth_storey@carleton.ca.

Abstract

BACKGROUND:

The insulin signaling pathway functions as a major regulator of many metabolic and cellular functions, and has been shown to be reversibly suppressed in many species during hibernation. This study characterized the regulation of PTEN phosphatase, a negative regulator of the insulin receptor network, over the torpor-arousal cycle of hibernation in the skeletal muscle of Ictidomys tridecemlineatus.

METHODS:

Western blotting and RT-PCR were used to analyze post-translational and transcriptional regulations of PTEN respectively. Enzymatic activities were determined by the malachite green assay, while protein stability was assessed the using pulse-proteolysis method.

RESULTS:

During torpor, the ratio of non-phosphorylated PTEN (S380/T382/T383) was significantly elevated by 1.4-fold during late torpor compared with euthermic controls; this was coupled with an increase in substrate affinity for PIP3 (by 56%) in late torpor. Two proteolytic cleavage PEST motifs were identified in the C-terminus that overlapped with the phosphorylation sites of PTEN; pulse-proteolysis analysis of PTEN protein showed a decrease in protein stability during late torpor (Cm of urea decreased by 21%). Furthermore, the increase in PTEN activity observed was correlated with a decrease in PDK-1 phosphorylation by 32%, suggesting a downstream effect of PTEN activation during torpor. Transcriptional analysis showed that mRNA expression of pten and pdk-1 remain unchanged during hibernation, suggesting post-translation modification as the primary regulatory mechanism of PTEN function.

CONCLUSION:

Phosphorylation plays an important role in the regulation of PTEN enzymatic activity and protein stability.

GENERAL SIGNIFICANCE:

Activation of PTEN during torpor can regulate insulin signaling during periods of low energy state.

KEYWORDS:

Ground squirrels; Hibernation; Insulin signaling pathway; Phosphorylation; Protein phosphatase

PMID:
26189697
DOI:
10.1016/j.bbagen.2015.07.004
[Indexed for MEDLINE]

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