Protein tyrosine and serine-threonine phosphatases in the sea urchin, Strongylocentrotus purpuratus: Identification and potential functions

Protein phosphatases, in coordination with protein kinases, play crucial roles in regulation of signaling pathways. To identify protein tyrosine phosphatases (PTPs) and serine-threonine (ser-thr) phosphatases in the Strongylocentrotus purpuratus genome, 179 annotated sequences were studied (122 PTPs, 57 ser-thr phosphatases). Sequence analysis identified 91 phosphatases (33 conventional PTPs, 31 dual specificity phosphatases, 1 Class III Cysteine-based PTP, 1 Asp-based PTP, and 25 ser-thr phosphatases). Using catalytic sites, levels of conservation and constraint in amino acid sequence were examined. Nine of 25 receptor PTPs (RPTPs) corresponded to human, nematode, or fly homologues. Domain structure revealed that sea urchin-specific RPTPs including two, PTPRLec and PTPRscav, may act in immune defense. Embryonic transcription of each phosphatase was recorded from a high-density oligonucleotide tiling microarray experiment. Most RPTPs are expressed at very low levels, whereas nonreceptor PTPs (NRPTPs) are generally expressed at moderate levels. High expression was detected in MAP kinase phosphatases (MKPs) and numerous ser-thr phosphatases. For several expressed NRPTPs, MKPs, and ser-thr phosphatases, morpholino antisense-mediated knockdowns were performed and phenotypes obtained. Finally, to assess roles of annotated phosphatases in endomesoderm formation, a literature review of phosphatase functions in model organisms was superimposed on sea urchin developmental pathways to predict areas of functional activity.