VHY, a Novel Myristoylated Testis-restricted Dual Specificity Protein Phosphatase Related to VHX

Abstract

The human DUSP15 gene encodes an uncharacterized 235-amino acid member of the subfamily of small dual specificity protein phosphatases related to the Vaccinia virus VH1 phosphatase. Similar to VHR-related MKPX (VHX) (DUSP22), the predicted protein has an N-terminal myristoylation recognition sequence, and we show here that both are indeed modified by the attachment of a myristate to Gly-2. In recognition of this relatedness to VHX, we refer to the DUSP15-encoded protein as VH1-related member Y (VHY). We report that VHY is expressed at high levels in the testis and barely detectable levels in the brain, spinal cord, and thyroid. A VHY-specific antiserum detected a protein with an apparent molecular mass of 26 kDa, and histochemical analysis showed that VHY was readily detectable in pachytene spermatocytes (midstage of meiotic division I) and round spermatids and weakly in Leydig cells (somatic cells outside of the seminiferous tubules). When expressed in 293T or NIH-3T3 cells, VHY was concentrated at the plasma membrane with some staining of vesicular structures in the Golgi region. Mutation of the myristoylation site Gly-2 abrogated membrane location. Finally, we demonstrate that VHY is an active phosphatase in vitro. We conclude that VHY is a new member of a subgroup of myristoylated VH1-like small dual specificity phosphatases.Phosphate is removed from phosphoproteins by several unrelated classes of protein phosphatases, including the serine/ threonine-specific phosphatases (PP1, PP2, etc.) 1 and three families of cysteine-based protein tyrosine phosphatases (PTPs) (reviewed in Refs. 1-3). There is also a newly discovered family of metal ion-dependent aspartic acid-based PTPs represented by the four Eyes Absent proteins (4 -6). The largest family of cysteine-based (7) phosphatases is made up of those related to the first sequenced PTP, PTP1B (8), and the receptor-like enzyme, CD45. Within this family are also 19 phosphatases with predominantly nonprotein substrates, 17 of them specific for the D3-phosphate of inositol phospholipids (9, 10) and two acting on RNA during the mRNA capping process (11,12). Another subgroup of 38 enzymes, referred to as the "classical" PTPs (13), have a deep catalytic pocket (ϳ9 Å), which only allows the long side chain of phosphotyrosine to reach the catalytic machinery (14). Accordingly, these PTPs are strictly tyrosine-specific. Other members of the PTP family have a more shallow catalytic pocket, and many of them dephosphorylate both phosphoserine/threonine and phosphotyrosine residues, at least in vitro (15)(16)(17)(18)(19)(20). These "dual specificity" phosphatases (DSPs) include the 11 MAP kinase phosphatases (MKPs) that dephosphorylate the mitogen-activated protein kinases Erk, Jnk, and p38 (21, 22) at their dually phosphorylated TXY activation loop motif.Another subgroup of DSPs, which we have referred to as the "atypical" DSPs (22) (as opposed to the "typical" DSPs, the MKPs), includes a number of poorly known enzymes that lack specific MAP kinase-targeting motifs and tend...

DUSP22/LMW-DSP2 regulates estrogen receptor-α-mediated signaling through dephosphorylation of Ser-118

“…However, we could not observe any significant alteration of ERa activation by expression of DUSP19, suggesting that DUSP22 specifically acts ERa-mediated signaling. Importantly, DUSP22 has been shown to be modified by the attachment of a myristate to the N-terminal Gly-2 (Alonso et al, 2004). Therefore, N-terminally tagged DUSP22 constructs lacks myristoylation of Gly-2 (Alonso et al, 2002).…”

“…This gene is now designated as DUSP22. DUSP22 has been also demonstrated to belong to a new subgroup of small DSPs anchored at the membranes by an N-terminal myristic acid moiety (Alonso et al, 2004). However, the physiological function of LMW-DSPs has remained unclear as it seems to be less efficient than many other MAPK-specific DSPs.…”

Regulation of STAT3-mediated signaling by LMW-DSP2

“…Dual specificity phosphatases (DSPs)/MAP kinase phosphatases (MKPs) are known to regulate MAP kinase-mediated signaling pathways, including ERK, JNK or p38 MAPK (Alonso et al, 2003). In previous studies, we cloned a distinct class of low molecular weight DSPs (LMW-DSPs) Aoyama et al, 2001) that contain a single catalytic domain, but lack a putative common docking site for MAPKs, designated the cdc25 homology domain.…”

Emerging Roles of Atypical Dual Specificity Phosphatases in Cancer

“…DUSP15 displays phosphatase activity against the artificial substrate pNPP in vitro [130], but physiological substrates for DUSP15 have yet to be reported. DUSP15 contains an N-terminal myristoylation signal, resulting in targeting of the protein to plasma membrane [90] and in mice DUSP15 has been identified as a candidate gene in a quantitative trait locus (QTL) thought to harbor genes that control for the predisposition to growth and fatness in mice [131].…”