title: COOH-terminal sequence motifs target the T cell protein tyrosine phosphatase to the ER and nucleus.
abstract: The noncatalytic domain of the human T cell protein tyrosine phosphatase (TCPTP) is alternatively spliced to generate a 45-kD form, p45TC, and a 48-kD form, p48TC (Champion-Arnaud et al., 1991; Mosinger et al., 1992). This manuscript concerns structural motifs in the noncatalytic segment of the enzyme responsible for targeting the two forms to different subcellular compartments. Endogenous and transiently expressed p48TC associates with the ER, as determined by sucrose gradient fractionation and indirect immunofluorescence, respectively. By contrast, p45TC localizes in the nucleus even though upon cell lysis it is not retained and fractionates with markers for soluble enzymes. Using fusion proteins consisting of beta-galactosidase and COOH-terminal fragments of p48TC, two motifs necessary for ER retention within a 70-residue targeting segment have been identified. These include the terminal 19 hydrophobic residues which comprise a potential membrane-spanning segment and residues 346-358 which encompass a cluster of basic amino acids that may represent another type of ER retention motif. The sequence RKRKR, which immediately precedes the splice junction, functions as a nuclear localization signal for p45TC.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle 98195, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Lorenzen
authors.forename: C Y
authors.initials: CY
authors.lastname: Dadabay
authors.forename: E H
authors.initials: EH
authors.lastname: Fischer
mesh_terms: D017398:Alternative Splicing / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells / Q000502:physiology; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism / Q000502:physiology*; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000166:cytology; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats
chemical_list: C516649:PTPN2 protein, human; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases; C516654:Ptpn2 protein, rat