Deactivation of sphingosine kinase 1 by protein phosphatase 2A.
Sphingosine kinase 1 (SK1) is an important regulator of cellular signaling that has been implicated in a broad range of cellular processes. Cell exposure to a wide array of growth factors, cytokines, and other cell agonists can result in a rapid and transient increase in SK activity via an activating phosphorylation. We have previously identified extracellular signal-regulated kinases 1 and 2 (ERK1/2) as the kinases responsible for the phosphorylation of human SK1 at Ser(225), but the corresponding phosphatase targeting this phosphorylation has remained undefined. Here, we provide data to support a role for protein phosphatase 2A (PP2A) in the deactivation of SK1 through dephosphorylation of phospho-Ser(225). The catalytic subunit of PP2A (PP2Ac) was found to interact with SK1 using both GST-pulldown and coimmunoprecipitation analyses. Coexpression of PP2Ac with SK1 resulted in reduced Ser(225) phosphorylation of SK1 in human embryonic kidney (HEK293) cells. In vitro phosphatase assays showed that PP2Ac dephosphorylated both recombinant SK1 and a phosphopeptide based on the phospho-Ser(225) region of SK1. Finally, both basal and tumor necrosis factor-alpha-stimulated cellular SK1 activity were regulated by molecular manipulation of PP2Ac activity. Thus, PP2A appears to function as an endogenous regulator of SK1 phosphorylation.
Hanson Institute, Division of Human Immunology, Institute of Medical and Veterinary Science, University of Adelaide, Adelaide, Australia.
Renae K
RK
Barr
Helen E
HE
Lynn
Paul A B
PA
Moretti
Yeesim
Y
Khew-Goodall
Stuart M
SM
Pitson
D000818:Animals; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020868:Gene Silencing; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D018482:Muscle, Skeletal / Q000201:enzymology; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012694:Serine / Q000737:chemistry; D013347:Subcellular Fractions / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099157:Sphingosine Kinase
D048049:Extracellular Signal-Regulated MAP Kinases; D005982:Glutathione Transferase; D017853:Phosphotransferases (Alcohol Group Acceptor); D054648:Protein Phosphatase 2; D012694:Serine; D014409:Tumor Necrosis Factor-alpha; D000099157:Sphingosine Kinase