Multiple dual specificity protein tyrosine phosphatases are expressed and regulated differentially in liver cell lines.
An emerging subclass of protein-tyrosine phosphatases (PTPases) exhibits sequence identity to the vaccinia H-1 (VH-1) gene product. These VH-1-like PTPases possess the canonical HCXAGXXR(S/T) sequence common to all PTPases, but unlike other PTPases they exhibit dual catalytic activity toward phosphotyrosine and nearby phosphothreonine residues in substrate proteins. We have isolated a novel VH-1-like PTPase, hVH-3, from the human placenta and compared various aspects of its expression with previously isolated members of this subfamily. The mammalian members of this subfamily including hVH-3 commonly localize to the nucleus and exhibit catalytic activity toward phosphorylated extracellular signal-regulated kinase. However, while the expression of some VH-1-like PTPases is extremely transient and independent of protein synthesis, hVH-3 expression is sustained over 3 h after being cell stimulated. Tissue-specific expression of hVH-3 is also distinct from other VH-1-like PTPases. Although VH-1-like PTPases have overlapping substrate specificity, there are differences in their mRNA regulation, response to extracellular stimuli, and tissue-specific expression, suggesting they serve specific roles in cellular function.
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606.
S P
SP
Kwak
J E
JE
Dixon
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA; D015971:Gene Expression Regulation, Enzymologic; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008969:Molecular Sequence Data; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D004247:DNA; D017027:Protein Tyrosine Phosphatases