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Title: THE AMP-ACTIVATED PROTEIN KINASE PATHWAY IN THE CHICKEN

Author
item Proszkowiec-Weglarz, Monika
item Richards, Mark

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 4/25/2005
Publication Date: 5/12/2005
Citation: Proszkowiec-Weglarz, M., Richards, M.P. 2005. The amp-activated protein kinase pathway in the chicken. BARC Poster Day.

Interpretive Summary:

Technical Abstract: In mammals, AMP-activated protein kinase (AMPK) is an enzyme complex that plays a key role in sensing cellular energy (AMP/ATP) levels, maintaining intracellular energy homeostasis and, on the whole animal level, in regulating energy balance and food intake. The AMPK protein complex is hetero-trimeric consisting of one catalytic (alpha) subunit and two regulatory (beta and gamma) subunits. AMPK is activated through phosphorylation by an upstream kinase (LKB1). Activated AMPK phosphorylates a variety of protein targets that affect carbohydrate, protein, and lipid metabolism. In general, AMPK acts to increase cellular energy level by reducing the activity of ATP-utilizing metabolic pathways and increasing those that generate ATP. Because the chicken is a important agricultural species and considering that a first draft of the chicken genome sequence has recently been completed, we were interested in verifying the existence of the AMPK pathway in chickens and in studying its function. Until now, there have been no reports of the AMPK cascade in any avian species. We have identified seven distinct chicken AMPK gene homologues for alpha, beta and gamma subunits. A molecular cloning strategy employing primer-directed reverse transcription polymerase chain reaction (RT-PCR) was devised to identify and characterize AMPK subunit gene transcripts expressed in different tissues obtained from 3-week-old male broiler chickens. Tissue-specific expression patterns for individual AMPK subunit genes were observed. Quantitative analysis of gene expression conducted by RT-PCR and capillary electrophoresis with laser-induced fluorescence detection showed that liver, brain, kidney, spleen, pancreas, duodenum, abdominal fat and hypothalamus expressed alpha-1, beta-2 and gamma-1 preferentially. Heart expressed alpha-2, beta-2 and gamma-1, whereas skeletal muscle expressed alpha-2, beta-2 and gamma-3. Moreover, the gamma-3 gene was only expressed in heart and skeletal muscle. We have also verified the expression of LKB1 and associated genes (MO25 and STRAD) in each of the tissues expressing AMPK subunits. The chicken gene homologues of LKB1, MO25 alpha and beta and STRAD beta were expressed in all tissues examined, whereas the STRAD alpha gene was exclusively expressed in brain, hypothalamus, heart and skeletal muscle. During changes in energy balance (24-48 h of food deprivation followed by refeeding) we did not observe any major changes in AMPK subunit or LKB1gene transcripts. Taken together, the expression of these genes suggests the existence of a functional AMPK pathway in chickens similar to that in mammals.