Thyroid hormone responsive protein Spot14 enhances catalysis of fatty acid synthase in lactating mammary epithelium.
Thyroid hormone responsive protein Spot 14 has been consistently associated with de novo fatty acid synthesis activity in multiple tissues, including the lactating mammary gland, which synthesizes large quantities of medium chain fatty acids (MCFAs) exclusively via FASN. However, the molecular function of Spot14 remains undefined during lactation. Spot14-null mice produce milk deficient in total triglyceride and de novo MCFA that does not sustain optimal neonatal growth. The lactation defect was rescued by provision of a high fat diet to the lactating dam. Transgenic mice overexpressing Spot14 in mammary epithelium produced total milk fat equivalent to controls, but with significantly greater MCFA. Spot14-null dams have no diminution of metabolic gene expression, enzyme protein levels, or intermediate metabolites that accounts for impaired de novo MCFA. When [(13)C] fatty acid products were quantified in vitro using crude cytosolic lysates, native FASN activity was 1.6-fold greater in control relative to Spot14-null lysates, and add back of Spot14 partially restored activity. Recombinant FASN catalysis increased 1.4-fold and C = 14:0 yield was enhanced 4-fold in vitro following addition of Spot14. These findings implicate Spot14 as a direct protein enhancer of FASN catalysis in the mammary gland during lactation when maximal MCFA production is needed.
Program in Molecular Biology, University of Colorado Anschutz Medical Campus, Aurora, CO Departments of Pathology University of Colorado Anschutz Medical Campus, Aurora, CO.
Michael C
MC
Rudolph
Departments of Pathology University of Colorado Anschutz Medical Campus, Aurora, CO.
Elizabeth A
EA
Wellberg
Departments of Pathology University of Colorado Anschutz Medical Campus, Aurora, CO.
Andrew S
AS
Lewis
Departments of Pathology University of Colorado Anschutz Medical Campus, Aurora, CO.
Kristina L
KL
Terrell
Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO.
Andrea L
AL
Merz
School of Pharmacy, University of Colorado Anschutz Medical Campus, Aurora, CO.
N Karl
NK
Maluf
Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO.
Natalie J
NJ
Serkova
Program in Molecular Biology, University of Colorado Anschutz Medical Campus, Aurora, CO Departments of Pathology University of Colorado Anschutz Medical Campus, Aurora, CO.
Steven M
SM
Anderson
D000818:Animals; D002384:Catalysis; D054890:Fatty Acid Synthase, Type I / Q000235:genetics / Q000378:metabolism*; D005260:Female; D007774:Lactation / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D009687:Nuclear Proteins; C501477:Thrsp protein, mouse; D014157:Transcription Factors; D054890:Fatty Acid Synthase, Type I
[13C] fatty acid quantification; fatty acid synthase catalysis; lactation; medium chain fatty acids