Role of A kinase anchor proteins in the tissue-specific regulation of lipoprotein lipase.
Activation of protein kinase A by catecholamines inhibits lipoprotein lipase (LPL) activity through the elaboration of an RNA binding complex, which inhibits LPL translation by binding to the 3'-untranslated region of the LPL mRNA. To better define this process, we reconstituted the inhibitory RNA binding complex in vitro and demonstrated that the K homology (KH) domain of A kinase anchor protein (AKAP) 121/149 plays a vital role in the inhibition of LPL translation. Inhibition of LPL translation occurred in vitro only when the Calpha subunit, R subunit, and AKAP 149 were present. Using different glutathione-S-transferase fusion proteins of AKAP 149, sequences containing the KH domain were required for inhibition of LPL translation, and the inhibition of AKAP 121 expression in 3T3-F442A adipocytes with short interfering RNA resulted in loss of epinephrine-mediated translation inhibition. After epinephrine injection into mice, LPL activity was inhibited in white adipose tissue but not in brown adipose tissue (BAT) or muscle. LPL activity and synthetic rate were inhibited in vitro by the addition of epinephrine to 3T3-F442A adipocytes, but there was no effect in L6 muscle cells and cultures of brown adipocytes. Corresponding with these differences in LPL translation, AKAP 121 protein and mRNA were abundantly expressed in mouse white adipose tissue, but was either very low or undetectable in BAT and muscle. Thus, AKAP 121/149 contains a KH region that is essential to the translation inhibition of LPL in response to epinephrine. BAT and muscle do not express significant AKAP 121/149, and this likely explains some of the tissue-specific differences in LPL regulation.
Ranganathan
Gouri
G
The Central Arkansas Veterans Healthcare System, and Department of Medicine, Division of Endocrinology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. Ranganathangouri@uams.edu
Pokrovskaya
Irina
I
Ranganathan
Subramanian
S
Kern
Philip A
PA
D016475:3T3 Cells; D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; C486333:Akap1 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D008071:Lipoprotein Lipase; D004837:Epinephrine