DUSP22 Human

What is DUSP22 and what are its main functions in human cells?

DUSP22 is an atypical phosphatase consisting of 184 amino acid residues that is widely expressed across various human tissues. It belongs to the dual-specificity phosphatase family, with the ability to dephosphorylate both tyrosine and serine/threonine residues. DUSP22 is also known as JKAP (JNK pathway-associated phosphatase) due to its role in regulating the JNK pathway .

The main functions of DUSP22 include:

• Dephosphorylation of multiple substrates including P38/MAPK, JNK/MAPK, estrogen receptor (ER), focal adhesion kinases (FAK), lymphocyte-specific protein tyrosine kinase, and signal transducer and activator of transcription 3 (STAT3)

• Regulation of T-cell receptor signaling

• Modulation of muscle cell differentiation and myofiber development

• Control of endothelial-to-mesenchymal transition (EndMT)

What signaling pathways are regulated by DUSP22?

DUSP22 interacts with and regulates several major signaling pathways:

• MAPK Signaling Pathway: DUSP22 dephosphorylates both P38/MAPK and JNK/MAPK, serving as a negative regulator of these pathways . In skeletal muscle, this regulation appears critical for preventing atrophy through a DUSP22-JNK-FOXO3a signaling axis .

• Smad2/3 Pathway: In endothelial cells, DUSP22 regulates the Smad2/3 pathway, which plays a crucial role in EndMT .

• FOXO3a Signaling: DUSP22 targeting downregulates genes linked to FOXO3a signaling, including key atrophy genes atrogin-1 and MuRF-1, as shown by RNA sequencing analysis of targeted aged muscle .

• PI3K-Akt Pathway: Pharmacological targeting of DUSP22 has been shown to affect genes linked to the PI3K-Akt pathway, suggesting regulatory influence in this critical growth and survival pathway .

How is DUSP22 expression altered in pathological conditions?

DUSP22 expression undergoes significant alterations in several pathological conditions:

• Skeletal Muscle Wasting: DUSP22 is upregulated in various muscle wasting conditions including:

  • Age-related sarcopenia

  • Dexamethasone-induced muscle atrophy

  • Immobilization-induced muscle atrophy, where DUSP22 expression inversely correlates with muscle mass

• Endothelial Dysfunction: In the transforming growth factor-β-induced EndMT model using human umbilical vein endothelial cells (HUVECs), DUSP22 expression is downregulated . This downregulation appears to contribute to EndMT progression, while DUSP22 overexpression ameliorates EndMT .

• Other Diseases: DUSP22 dysregulation has been linked to T-cell lymphoma and Alzheimer's disease, though the exact mechanisms require further investigation .

How does DUSP22 modulate skeletal muscle atrophy at the molecular level?

DUSP22 modulates skeletal muscle atrophy through several interconnected molecular mechanisms:

• JNK-FOXO3a Signaling Axis: DUSP22 regulates a DUSP22-JNK-FOXO3a signaling axis. Pharmacological targeting or knockdown of DUSP22 inhibits this pathway, leading to downregulation of atrophy-related genes .

• Atrogene Regulation: DUSP22 targeting downregulates key atrogenes:

  • Atrogin-1 (MAFbx): A muscle-specific ubiquitin ligase upregulated during atrophy

  • MuRF-1: A muscle RING-finger protein involved in ubiquitin-mediated proteolysis

• Mitochondrial Function Modulation: DUSP22 overexpression affects mitochondrial function by:

  • Downregulating PGC-1α, a master regulator of mitochondrial biogenesis

  • Upregulating UCP-3, a mitochondrial uncoupling protein

• Autophagy Pathway Activation: DUSP22 overexpression upregulates autophagy genes, including:

  • LC-3B (microtubule-associated proteins 1A/1B light chain 3B)

  • Ctsl (cathepsin L1)

• Ubiquitin-Proteasome System (UPS) Regulation: DUSP22 overexpression upregulates UBR2 (ubiquitin protein ligase E3 component N-recognin 2), a component of the UPS .

What transcriptional changes occur following DUSP22 pharmacological targeting in aged muscle?

RNA sequencing analysis of tibialis anterior (TA) muscle in geriatric mice (27 months-old) revealed significant transcriptional changes following DUSP22 pharmacological targeting with BML-260:

• Global Gene Expression Changes:

  • 350 differentially expressed genes (DEGs) were identified

  • Principal component analysis showed consistent effects of BML-260 on gene expression in aged mice

• FOXO3a Signaling:

  • Downregulation of genes linked to FOXO3a signaling, including atrogin-1 and MuRF-1

• Myokine Expression:

  • Upregulation of musclin (OSTN), an exercise-induced myokine that protects against muscle wasting

• Muscle Cell Differentiation and Development:

  • Upregulation of genes linked to muscle cell differentiation and muscle fiber development

  • Increased expression of Myh4 (myosin heavy chain 2b), predominant in fast-twitch muscle

  • Upregulation of Six1 and Six4, which activate fast-type muscle gene programs

• PI3K-Akt Pathway:

  • Downregulation of genes linked to the PI3K-Akt pathway

• Gene Set Enrichment Analysis (GSEA):

  • Under-representation of genes involved in negative regulation of hypertrophy and response to inactivity

  • Enrichment of genes involved in skeletal muscle cell differentiation and proliferation

How does DUSP22 influence endothelial-to-mesenchymal transition in cardiovascular disease models?

DUSP22 plays a regulatory role in endothelial-to-mesenchymal transition (EndMT), a process implicated in cardiovascular diseases such as cardiac hypertrophy, myofibrosis, cardiac remodeling, and heart failure:

• Expression Patterns During EndMT:

  • DUSP22 expression is downregulated during TGF-β-induced EndMT in human umbilical vein endothelial cells (HUVECs)

  • This downregulation correlates with phenotypic changes characteristic of EndMT

• Effect on Endothelial and Mesenchymal Markers:

  • During DUSP22 downregulation, expression of endothelial cell markers (CD31, VE-cadherin, E-cadherin, VEGF) decreases

  • Simultaneously, mesenchymal cell markers (α-SMA, vimentin, N-cadherin, FSP1, fibronectin) increase

• Signaling Pathway Regulation:

  • DUSP22 regulates EndMT through both the Smad2/3 and MAPK signaling pathways

  • Verification using signaling pathway inhibitors confirmed these regulatory mechanisms

• Functional Consequences:

  • DUSP22 deficiency aggravates EndMT

  • Conversely, DUSP22 overexpression ameliorates EndMT

  • DUSP22 downregulation enhances HUVEC migration rates following TGF-β induction

What is the mechanism of action of BML-260 as a DUSP22 inhibitor?

BML-260 is a small molecule inhibitor that targets DUSP22 with several notable characteristics:

• Chemical Structure and Properties:

  • Based on the rhodanine (2-thioxothiazolidin-4-one) chemical scaffold

  • Rhodanine is classified as a privileged heterocyclic compound amenable to structural modification

  • The compound has a yellow color and can interact photometrically in biological assessments

• Molecular Docking:

  • Binding of BML-260 to human DUSP22 has been analyzed with CB-Dock2 software

  • The Vina score was calculated using human DUSP22 (PDB: 6lvq) and BML-260 (CID: 1565747)

• Functional Effects in Skeletal Muscle:

  • BML-260 treatment increases mean body weight in dexamethasone-treated mice

  • Improves muscle performance in both acceleration and constant rotarod testing models

  • Increases myofiber cross-sectional area (CSA) and shifts myofiber area distribution toward larger sized fibers

  • Increases tibialis anterior muscle mass

  • Inhibits upregulation of atrogin-1 and MuRF-1

• Effects in Human Skeletal Muscle Cells:

  • BML-260 treatment recovers mean myotube diameter and increases proportion of larger myotubes in dexamethasone-induced atrophy models

  • Inhibits MuRF-1 expression in human myotubes

What in vitro models are appropriate for studying DUSP22 function?

Several in vitro models have been validated for DUSP22 research:

• Murine C2C12 Myoblast/Myotube System:

  • Growth conditions: DMEM with 10% fetal bovine serum and 1% penicillin/streptomycin

  • Differentiation protocol: Culture in DMEM with 2% horse serum for 96 hours

  • Atrophy induction: Treatment with 10 μM dexamethasone for 24 hours

  • Readouts: Myotube diameter, fusion index, differentiation index, gene expression analysis

• Human Skeletal Myoblast System:

  • Commercial human skeletal myoblasts (available from Thermo-Fisher Scientific)

  • Differentiation: Culture in differentiation media for 72 hours

  • Atrophy induction: Treatment with 10 μM dexamethasone for 24 hours

  • Analysis: H&E staining, myotube diameter measurement via light microscopy

• Human Umbilical Vein Endothelial Cells (HUVECs):

  • EndMT induction: Stimulation with 10 ng/ml TGF-β for 48 hours

  • Phenotypic characterization: Assessment of endothelial markers (CD31, VE-cadherin, E-cadherin, VEGF) and mesenchymal markers (α-SMA, vimentin, N-cadherin, FSP1, fibronectin)

  • Functional assessment: Cell migration assays

What genetic manipulation approaches are effective for DUSP22 studies?

Several genetic manipulation techniques have been successfully employed in DUSP22 research:

• CRISPR-Cas9 Gene Editing:

  • Used for DUSP22 overexpression in C2C12 myoblasts

  • Confirmation of editing efficiency via qPCR

  • Enables assessment of effects on myotube formation, fusion index, and differentiation index

• siRNA Knockdown:

  • In vitro: Effective for DUSP22 knockdown in cell culture models

  • In vivo: Intramuscular delivery using Invivofectamine 3.0 reagent

  • Protocol for aged mice: 35 μg siRNA complexes injected into TA muscle, with a second injection 4 days later, and analysis at day 10

  • Verification: qPCR confirmation of knockdown efficiency

• Plasmid-Based Overexpression:

  • Used for DUSP22 overexpression studies in HUVECs

  • Allows assessment of EndMT phenotype reversal

What in vivo models are most effective for studying DUSP22 in disease contexts?

Multiple in vivo models have been validated for studying DUSP22's role in disease:

• Dexamethasone-Induced Muscle Atrophy Model:

  • Dexamethasone treatment induces muscle wasting

  • Useful for testing pharmacological agents

  • Metrics: Body weight, grip strength, rotarod performance, muscle histology, gene expression

• Aging-Related Sarcopenia Model:

  • Geriatric mice (24-27 months old)

  • Allows study of age-related muscle wasting

  • Compatible with both genetic (siRNA) and pharmacological (BML-260) interventions

  • Treatment protocol: 5 mg/kg BML-260 via intraperitoneal delivery every 24h for 4 weeks

• Hind Limb Immobilization Model:

  • 14-week-old male C57BL/6 mice with immobilized hind limbs using plastic EP-tubes

  • Immobilization period: 14 days

  • Allows study of disuse-induced muscle atrophy

  • Compatible with pharmacological intervention (5 mg/kg BML-260)

What is the therapeutic potential of DUSP22 targeting in human diseases?

DUSP22 targeting shows promising therapeutic potential across multiple human diseases:

• Skeletal Muscle Wasting Disorders:

  • Effective in multiple models of muscle wasting including aging-related sarcopenia, dexamethasone-induced atrophy, and immobilization-induced atrophy

  • BML-260 prevents muscle wasting via inhibition of the DUSP22-JNK-FOXO3a signaling axis

  • Efficacy demonstrated in human donor-derived skeletal muscle cells, suggesting translational potential

• Cardiovascular Diseases:

  • DUSP22 overexpression ameliorates endothelial-to-mesenchymal transition (EndMT)

  • Potential relevance for cardiac hypertrophy, myofibrosis, cardiac remodeling, and heart failure

  • The identified DUSP22 regulatory role in EndMT may lead to new therapeutic strategies

• Other Potential Indications:

  • Previous research has linked aberrant DUSP22 to T-cell lymphoma and Alzheimer's disease

  • May be relevant to other aging-related disorders such as osteoarthritis and type 2 diabetes

  • Potential role in depression via regulation of musclin, a myokine shown to alleviate depressive symptoms in animal models

What biomarkers can be used to assess the efficacy of DUSP22-targeted interventions?

Several biomarkers have been validated for assessing DUSP22-targeted interventions:

• Molecular Biomarkers:

  • DUSP22 expression levels (measured by qPCR or western blot)

  • Atrogene expression (atrogin-1, MuRF-1) as indicators of muscle atrophy pathways

  • JNK and FOXO3a phosphorylation status as indicators of pathway activation

  • Musclin (OSTN) levels as indicator of anti-atrophic response

• Functional/Physiological Biomarkers:

  • Muscle mass measurements (individual muscle weights)

  • Myofiber cross-sectional area distributions

  • Grip strength as indicator of muscle function

  • Rotarod performance (acceleration and constant models)

• Histological Markers:

  • Myofiber type distribution (fast vs. slow twitch fibers)

  • Myotube diameter in cell culture models

  • Expression of endothelial vs. mesenchymal markers in EndMT models

What are the most promising avenues for DUSP22 drug development?

Several promising approaches for DUSP22-targeted drug development emerge from current research:

• Rhodanine-Based Scaffold Optimization:

  • BML-260 is based on the rhodanine (2-thioxothiazolidin-4-one) chemical scaffold

  • This scaffold is amenable to structural modification and lead development

  • Further rounds of structural optimization could improve drug-like properties, biological stability, and DUSP22 targeting specificity

• Theranostic Development:

  • Rhodanine's yellow color and photometric interaction potential in biological assessments suggests possible development as a theranostic agent

  • Could potentially serve as both a diagnostic biomarker and therapeutic drug for skeletal muscle wasting

• Alternative JNK Inhibition Strategies:

  • DUSP22 targeting represents an indirect approach to JNK inhibition

  • May circumvent limitations encountered with direct JNK inhibitors, none of which have yet achieved clinical approval despite extensive research

• Tissue-Specific Delivery Systems:

  • Development of targeted delivery systems for skeletal muscle or endothelial tissue could enhance efficacy while reducing off-target effects

  • Current in vivo studies use systemic (intraperitoneal) or local (intramuscular) delivery approaches

How might DUSP22's role in musclin regulation inform therapeutic approaches?

The discovery that DUSP22 targeting upregulates musclin expression opens interesting therapeutic possibilities:

• Cardio-Sarcopenia Applications:

  • Musclin has been shown to be critical for cardiac conditioning

  • Cardiac hypertrophy and skeletal muscle wasting share similar molecular mechanisms

  • Cardio-sarcopenia is recognized as a syndrome of concern in aging

  • DUSP22 targeting might address both cardiac and skeletal muscle aspects of aging-related decline

• Neuropsychiatric Applications:

  • Skeletal muscle-secreted musclin has recently been shown to alleviate depression in animal models

  • DUSP22 targeting might have unexplored potential in depressive disorders through musclin upregulation

  • This represents a novel link between muscle physiology and mental health

• Mechanistic Understanding:

  • Further research is needed to determine whether musclin levels are directly regulated by DUSP22 or via downstream effects on JNK-FOXO3a inhibition

  • Understanding this regulatory mechanism could inform more targeted therapeutic approaches