HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Data Buy All Versions of this Article: fj.08-120550v1 23/3/751    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mukhopadhyay, A. Articles by Ogretmen, B. Search for Related Content PubMed PubMed Citation Articles by Mukhopadhyay, A. Articles by Ogretmen, B.

Direct interaction between the inhibitor 2 and ceramide via sphingolipid-protein binding is involved in the regulation of protein phosphatase 2A activity and signaling

Archana Mukhopadhyay^*,, Sahar A. Saddoughi^*,, Pengfei Song^*,, Iyad Sultan^*,,1, Suriyan Ponnusamy^*,, Can E. Senkal^*,, Christopher F. Snook^*, Hugh K. Arnold, Rosalie C. Sears, Yusuf A. Hannun^*, and Besim Ogretmen^*,,2

^* Department of Biochemistry and Molecular Biology and

Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA; and

Department of Molecular Medical Genetics, Oregon Health and Sciences University, Portland, Oregon, USA

²Correspondence: Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas St., Charleston, SC 29425, USA. E-mail: ogretmen{at}musc.edu

In this study, the inhibitor 2 of protein phosphatase 2A (I2PP2A) was identified in vitro and in situ as a ceramide-binding protein, which exhibits stereoisomer specificity and fatty acid chain length preference. Site- directed mutagenesis coupled with structural details of I2PP2A suggested that VIK 207-209 residues localized on helix 7 are important for ceramide binding and single mutation of K209D altered this interaction. Notably, I2PP2A-ceramide binding decreased the association between PP2A and the inhibitor, preventing the inhibition of PP2A activity in vitro. In addition, studies in A549 human lung cancer cells revealed that ceramide mediates c-Myc degradation via its PP2A-dependent dephosphorylation at S62, and treatment with okadaic acid and expression of c-Myc mutants with S62A or S62D conversions resulted in resistance to ceramide-mediated degradation. Importantly, whereas down-regulation of I2PP2A enhanced PP2A-mediated c-Myc degradation in response to ceramide, ectopic expression of wild-type I2PP2A but not of its K209D mutant protected this degradation in A549 cells. Moreover, expression of wild-type I2PP2A prevented the growth-inhibitory effects of ceramide both against A549 cells and xenograft-driven tumors in situ and in vivo compared with that in controls. Thus, these results suggest that direct interaction of I2PP2A with ceramide plays important biological roles via the regulation of PP2A activity and signaling, which in turn control ceramide-mediated degradation of c-Myc and antiproliferation.—Mukhopadhyay, A., Saddoughi, S. A., Song, P., Sultan, I., Ponnusamy, S., Senkal, C. E., Snook, C. F., Arnold, H. K., Sears, R. C., Hannun, Y. A., Ogretmen, B. Direct interaction between the inhibitor 2 and ceramide via sphingolipid-protein binding is involved in the regulation of protein phosphatase 2A activity and signaling.

Key Words: bioactive lipids • c-Myc degradation

This article has been cited by other articles:

				J. L. McConnell and B. E. Wadzinski Targeting Protein Serine/Threonine Phosphatases for Drug Development Mol. Pharmacol., June 1, 2009; 75(6): 1249 - 1261. [Abstract] [Full Text] [PDF]