AI Article Synopsis
- The study identifies and characterizes the LKB1-MO25-STRAD complex in skeletal muscle for the first time, demonstrating its significance as the principal AMP-activated protein kinase kinase (AMPKK) complex.
- The researchers confirm the presence of this complex and establish the absence of mRNA splice variants in skeletal muscle.
- Quantitative PCR revealed reduced levels of LKB1, MO25α, and STRADβ mRNA in muscle samples lacking LKB1, reinforcing the role of this complex in muscle function.
Article Abstract
In liver, the AMP-activated protein kinase kinase (AMPKK) complex was identified as the association of liver kinase B1 (LKB1), mouse protein 25 (MO25α/β), and Ste-20-related adaptor protein (STRADα/β); however, this complex has yet to be characterized in skeletal muscle. We demonstrate the expression of the LKB1-MO25-STRAD complex in skeletal muscle, confirm the absence of mRNA splice variants, and report the relative mRNA expression levels of these proteins in control and muscle-specific LKB1 knockout (LKB1(-/-)) mouse muscle. LKB1 detection in untreated control and LKB1(-/-) muscle lysates revealed two protein bands (50 and 60 kDa), although only the heavier band was diminished in LKB1(-/-) samples [55 ± 2.5 and 13 ± 1.5 arbitrary units (AU) in control and LKB1(-/-), respectively, P < 0.01], suggesting that LKB1 is not represented at 50 kDa, as previously cited. The 60-kDa LKB1 band was further confirmed following purification using polyethylene glycol (43 ± 5 and 8.4 ± 4 AU in control and LKB1(-/-), respectively, P < 0.01) and ion-exchange fast protein liquid chromatography. Mass spectrometry confirmed LKB1 protein detection in the 60-kDa protein band, while none was detected in the 50-kDa band. Coimmunoprecipitation assays demonstrated LKB1-MO25-STRAD complex formation. Quantitative PCR revealed significantly reduced LKB1, MO25α, and STRADβ mRNA in LKB1(-/-) muscle. These findings demonstrate that the LKB1-MO25-STRAD complex is the principal AMPKK in skeletal muscle.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3233888 | PMC |
| http://dx.doi.org/10.1152/japplphysiol.00160.2011 | DOI Listing |
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