ToxSci Advance Access published online on February 16, 2006
Toxicological Sciences, doi:10.1093/toxsci/kfj135
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1 Division of Biological Sciences, CIIT Centers for Health Research, Research Triangle Park, NC 27709
* To whom correspondence should be addressed. Phthalates are ubiquitous environmental contaminants that target the fetal and pubertal testis leading to alterations in endocrine and spermatogenic function. Some features of phthalate induced testicular injury suggest that phthalates alter Sertoli-germ cell adhesion and G protein signaling. Celsr2 is a unique protein that has structural characteristics of both an adhesion molecule and a G protein coupled receptor (GPCR) and has been demonstrated to function in Sertoli-germ cell adhesion. Within two hours of a 1 g/kg MEHP exposure, in vivo Sertoli cell celsr2 localization was altered; celsr2 immunostaining became concentrated in the basal aspect of Sertoli cells and then a diffuse pattern emerged. Because GPCRs are regulated by phosphorylation, the hypothesis that phthalate exposure induces the phosphorylation of celsr2 was tested by examining phosphorylation in celsr2 transfected HeLa cells treated with mono-(2-ethylhexyl) phthalate (MEHP). At concentrations of 1 µM or greater, MEHP transiently increased celsr2 phosphorylation on serine/threonine residues; celsr2 phosphorylation was increased by 15 minutes of exposure and returned to control levels after 60 minutes. Cells exposed to the inactive phthalate monoester mono-methyl phthalate (MMP) showed no change in celsr2 phosphorylation. In addition, phosphorylation of the endogenous HeLa cell GPCR, CXCR4, was not altered by exposure to MEHP. Inhibition of protein kinase C or casein kinase 1 prevented MEHP-induced celsr2 phosphorylation, while inhibition of protein kinase A or mitogen-activated protein kinase had no effect. These data show that MEHP exposure rapidly alters testicular celsr2 immunolocalization as well as celsr2 post-translational modification in a model cell line.
Received November 4, 2005
Accepted February 13, 2006
Reproductive and Developmental Toxicology
Mono-(2-ethylhexyl) Phthalate Rapidly Increases Celsr2 Protein Phosphorylation in HeLa Cells Via Protein Kinase C and Casein Kinase 1
Stephanie A. Lahousse 1,
Stephanie Beall 2,
and
Kamin J. Johnson 1 *
2 Department of Pathology and Laboratory Medicine, Brown University, Providence, RI 02912
Kamin J. Johnson, E-mail: kjohnson{at}ciit.org
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