Pseudophosphatase MK-STYX Alters Histone Deacetylase 6 Cytoplasmic Localization, Decreases Its Phosphorylation, and Increases Detyrosination of Tubulin

Abstract

The catalytically inactive mitogen-activated protein (MAP) kinase phosphatase, MK-STYX (MAPK (mitogen-activated protein kinase) phosphoserine/threonine/tyrosine-binding protein) interacts with the stress granule nucleator G3BP-1 (Ras-GAP (GTPase-activating protein) SH3 (Src homology 3) domain-binding protein-1), and decreases stress granule (stalled mRNA) formation. Histone deacetylase isoform 6 (HDAC6) also binds G3BP-1 and serves as a major component of stress granules. The discovery that MK-STYX and HDAC6 both interact with G3BP-1 led us to investigate the effects of MK-STYX on HDAC6 dynamics. In control HEK/293 cells, HDAC6 was cytosolic, as expected, and formed aggregates under conditions of stress. In contrast, in cells overexpressing MK-STYX, HDAC6 was both nuclear and cytosolic and the number of stress-induced aggregates significantly decreased. Immunoblots showed that MK-STYX decreases HDAC6 serine phosphorylation, protein tyrosine phosphorylation, and lysine acetylation. HDAC6 is known to regulate microtubule dynamics to form aggregates. MK-STYX did not affect the organization of microtubules, but did affect their post-translational modification. Tubulin acetylation was increased in the presence of MK-STYX. In addition, the detyrosination of tubulin was significantly increased in the presence of MK-STYX. These findings show that MK-STYX decreases the number of HDAC6-containing aggregates and alters their localization, sustains microtubule acetylation, and increases detyrosination of microtubules, implicating MK-STYX as a signaling molecule in HDAC6 activity.

Pseudophosphatase MK‐STYX: the atypical member of the MAP kinase phosphatases

“…We found that HDAC6 localizes in both the cytosol and nucleus in the presence of MK‐STYX, instead of solely in the cytosol (Fig. 3A) [67]. In addition, HDAC6 phosphorylation at Ser 22 decreases in the presence of MK‐STYX (Fig.…”

“…In addition, HDAC6 phosphorylation at Ser 22 decreases in the presence of MK‐STYX (Fig. 3B) [67], illustrating that MK‐STYX influences HDAC6 dynamics in both its subcellular localization and post‐translational modification [67]. Thus, a strong link for the role of MK‐STYX in HDAC6 signaling has been established, and MK‐STYX as a regulator in the stress response pathway has been further supported, but how MK‐STYX inhibits stress granules remains elusive.…”

HDAC6 in Diseases of Cognition and of Neurons

“…How intracellular signaling affects HDAC6 is of paramount importance in order to implement effective approaches that modulate HDAC6 and intracellular transport. Cao et al [ 90 ] showed that MAPK (mitogen-activated protein kinase) regulates HDAC6 localization and phosphorylation, in addition to having positive effects on tyrosinated tubulin and microtubule (MT) stability.…”

“…The catalytically inactive MAP kinase phosphatase (MK-STYX) interacts with the stress granule nucleator G3BP-1 to decrease stress granule formation. Since MK-STYX is a signaling molecule along HDAC6 activity, future studies should explore in more detail the relationship between HDAC6i and stress granule regulation [ 90 ].…”

Dual Specificity Phosphatases: From Molecular Mechanisms to Biological Function

“…Circulating tumor cells play a major role in tumor dissemination and metastasis, and Wu et al reported the enrichment in nuclear localized DUSP6 in circulating tumor cells from triple negative breast cancers, as well as in brain metastases, suggesting a specific role for nuclear DUSP6 in cancer spreading [21]. Finally, Cao et al provided new insights into the functions of the catalytically inactive MK-STYX pseudophosphatase as an indirect regulator of post-translational modifications from proteins regulating microtubule dynamics, including histone deacetylase isoform 6 and tubulin [22].…”