Cloning of murine low molecular weight phosphotyrosine protein phosphatase cDNA: identification of a new isoform

• Published in: FEBS letters Vol. 437; no. 3; pp. 263 - 266
• Main Authors: Magherini, F, Giannoni, E, Raugei, G, Cirri, P, Paoli, P, Modesti, A, Camici, G, Ramponi, G
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 23.10.1998
• Subjects: 3T3 Cells; Alternative splicing; Amino Acid Sequence; Animals; Blotting, Northern; Cloning, Molecular; DNA, Complementary - isolation & purification; ERK, extracellular signal-regulated kinase; Escherichia coli - genetics; Humans; Isoenzymes - chemistry; Isoenzymes - genetics; Isoenzymes - isolation & purification; LMW-PTP, low molecular weight phosphotyrosine protein phosphatase; Mice; Molecular Sequence Data; Molecular Weight; Mouse; Phosphotyrosine protein phosphatase; pNPP, para-nitrophenyl phosphate; Protein Tyrosine Phosphatases - chemistry; Protein Tyrosine Phosphatases - genetics; Protein Tyrosine Phosphatases - isolation & purification; PTKs, protein tyrosine kinases; PTPs, protein tyrosine phosphatases; RACE, rapid amplification of cDNA ends; Rats; Recombinant Proteins - biosynthesis; RNA, Messenger - metabolism; STAT, signal transducer and activators of transcription; Alternative splicing; ERK, extracellular signal-regulated kinase; Mouse; pNPP, para-nitrophenyl phosphate; RACE, rapid amplification of cDNA ends; Phosphotyrosine protein phosphatase; LMW-PTP, low molecular weight phosphotyrosine protein phosphatase; PTPs, protein tyrosine phosphatases; PTKs, protein tyrosine kinases; STAT, signal transducer and activators of transcription
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(98)01241-1

The low molecular weight phosphotyrosine protein phosphatase (LMW-PTP) is a 18 kDa cytosolic enzyme, involved in the negative regulation of cell proliferation. In different mammalian species LMW-PTPs are expressed in two molecular forms produced from a single primary transcript through an alternative splicing mechanism. In this paper we report the cloning, expression and characterization of mouse isoforms of LMW-PTPs (called m-IF1 and m-IF2), very similar to the corresponding rat and human isoenzymes. Moreover we have identified a third cDNA encoding a protein (m-IF2P) that presents three substitutions compared to m-IF2. This new isoform is still active on pNPP, although to a lower extent: this reduction is mainly due to the leucine to proline substitution in position 13, within the catalytic loop. The mRNA expression level of this isoform is comparable to those of m-IF1 and m-IF2. It is likely that a gene duplication process followed by mutations has generated this new gene.