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Acetylation of heat shock protein 20 (Hsp20) regulates human myometrial activity.

ABSTRACT: Phosphorylation of heat shock protein 20 (Hsp20) by protein kinase A (PKA) is now recognized as an important regulatory mechanism modulating contractile activity in the human myometrium. Thus agonists that stimulate cyclic AMP production may cause relaxation with resultant beneficial effects on pathologies that affect this tissue such as the onset of premature contractions prior to term. Here we describe for the first time that acetylation of Hsp20 is also a potent post-translational modification that can affect human myometrial activity. We show that histone deacetylase 8 (HDAC8) is a non-nuclear lysine deacetylase (KDAC) that can interact with Hsp20 to affect its acetylation. Importantly, use of a selective linkerless hydroxamic acid HDAC8 inhibitor increases Hsp20 acetylation with no elevation of nuclear-resident histone acetylation nor marked global gene expression changes. These effects are associated with significant inhibition of spontaneous and oxytocin-augmented contractions of ex vivo human myometrial tissue strips. A potential molecular mechanism by which Hsp20 acetylation can affect myometrial activity by liberating cofilin is described and further high-lights the use of specific effectors of KDACs as therapeutic agents in regulating contractility in this smooth muscle.

SUBMITTER: Karolczak-Bayatti M

PROVIDER: S-EPMC3190820 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Acetylation of heat shock protein 20 (Hsp20) regulates human myometrial activity.

Karolczak-Bayatti Magdalena M Sweeney Michèle M Cheng Joanna J Edey Lydia L Robson Stephen C SC Ulrich Scott M SM Treumann Achim A Taggart Michael J MJ Europe-Finner G Nicholas GN

The Journal of biological chemistry 20110729 39

Phosphorylation of heat shock protein 20 (Hsp20) by protein kinase A (PKA) is now recognized as an important regulatory mechanism modulating contractile activity in the human myometrium. Thus agonists that stimulate cyclic AMP production may cause relaxation with resultant beneficial effects on pathologies that affect this tissue such as the onset of premature contractions prior to term. Here we describe for the first time that acetylation of Hsp20 is also a potent post-translational modificatio ...[more]

PMID: 21803775

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Project description:Small heat shock proteins (sHsps) are a ubiquitous part of the machinery that maintains cellular protein homeostasis by acting as molecular chaperones. sHsps bind to and prevent the aggregation of partially folded substrate proteins in an ATP-independent manner. sHsps are dynamic, forming an ensemble of structures from dimers to large oligomers through concentration-dependent equilibrium dissociation. Based on structural studies and mutagenesis experiments, it is proposed that the dimer is the smallest active chaperone unit, while larger oligomers may act as storage depots for sHsps or play additional roles in chaperone function. The complexity and dynamic nature of their structural organization has made elucidation of their chaperone function challenging. HspB1 and HspB5 are two canonical human sHsps that vary in sequence and are expressed in a wide variety of tissues. In order to determine the role of the dimer in chaperone activity, glutathione-S-transferase (GST) was genetically linked as a fusion protein to the N-terminus regions of both HspB1 and HspB5 (also known as Hsp27 and αB-crystallin, respectively) proteins in order to constrain oligomer formation of HspB1 and HspB5, by using GST, since it readily forms a dimeric structure. We monitored the chaperone activity of these fusion proteins, which suggest they primarily form dimers and monomers and function as active molecular chaperones. Furthermore, the two different fusion proteins exhibit different chaperone activity for two model substrate proteins, citrate synthase (CS) and malate dehydrogenase (MDH). GST-HspB1 prevents more aggregation of MDH compared to GST-HspB5 and wild type HspB1. However, when CS is the substrate, both GST-HspB1 and GST-HspB5 are equally effective chaperones. Furthermore, wild type proteins do not display equal activity toward the substrates, suggesting that each sHsp exhibits different substrate specificity. Thus, substrate specificity, as described here for full-length GST fusion proteins with MDH and CS, is modulated by both sHsp oligomeric conformation and by variations of sHsp sequences.

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Acetylation of heat shock protein 20 (Hsp20) regulates human myometrial activity.

Publications

Acetylation of heat shock protein 20 (Hsp20) regulates human myometrial activity.

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