11th Asia Oceania Human Proteome Organization Congress Report.

As the first in-person Asia Oceania Human Proteomics Organization (AOHUPO) congress since 2018, the 11th AOHUPO congress was an opportune time for the research community to reconnect and to renew friendships after the long period of restricted travel due to the global pandemic. Moreover, this congress was a great opportunity for the many AO regional proteomics and mass spectrometry scientists to meet in Singapore to exchange ideas and to present their latest findings. Cohosted by the Singapore Society for Mass Spectrometry and the Malaysian Proteomics Society and held in conjunction with the seventh Asia Oceania Agricultural Proteomics Organization Congress and Singapore Society for Mass Spectrometry 2023, the meeting featured both human and agricultural proteomics. Over five hundred scientists from the AO region converged on the MAX Atria @ Singapore EXPO, Changi, Singapore from May 8 to 10 for the main congress. The diverse program was made up of 64 invited speakers and panellists for seven plenary lectures, 27 concurrent symposia, precongress and postcongress workshops, and 174 poster presentations. The AOHUPO society were able to celebrate not only their 20th anniversary but also the outstanding academic research from biological and agricultural proteomics and related 'omics fields being conducted across the Asia-Oceania region.

NDUFA12 as a Functional Target of the Anticancer Compound Ertredin in Human Hepatoma Cells As Revealed by Label-Free Chemical Proteomics.

Many attempts have been made to develop new agents that target EGFR mutants or regulate downstream factors in various cancers. Cell-based screening showed that a natural small molecule, Ertredin, inhibited the growth of EGFRvIII mutant cancer cells. Previous studies have shown that Ertredin effectively inhibits anchorage-independent 3D growth of sphere-forming cells transfected with EGFRvIII mutant cDNA. However, the underlying mechanism remains unclear. In this study, we investigated the target protein of Ertredin by combining drug affinity-responsive target stability (DARTS) assays with liquid chromatography-mass spectrometry using label-free Ertredin as a bait and HepG2 cell lysates as a proteome pool. NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 12 (NDUFA12) was identified as an Ertredin-binding protein that was responsible for its biological activity. The interaction between NDUFA12 and Ertredin was validated by DARTS and cellular thermal shift assays. In addition, the genetic knockdown of the identified target, NDUFA12, was shown to suppress cell proliferation. NDUFA12 was identified as a biologically relevant target protein of Ertredin that is responsible for its antitumor activity, and these results provide insights into the role of NDUFA12 as a downstream factor in EGFRvIII mutants.

The Second Asia-Oceania Human Proteome Organization (AOHUPO) Online Education Series on the Renaissance of Clinical Proteomics: Biomarkers, Imaging and Therapeutics.

In 2021, the Asia-Oceania Human Proteome Organization (AOHUPO) initiated a new endeavor named the AOHUPO Online Education Series with the aim to promote scientific education and collaboration, exchange of ideas and culture among the young scientists in the AO region. Following the warm participation, the AOHUPO organized the second series in 2022, with the theme "The Renaissance of Clinical Proteomics: Biomarkers, Imaging and Therapeutics". This time, the second AOHUPO Online Education Series was hosted by the UKM Medical Molecular Biology Institute (UMBI) affiliated to the National University of Malaysia (UKM) in Kuala Lumpur, Malaysia on three consecutive Fridays (11th, 18th and 25th of March). More than 300 participants coming from 29 countries/regions registered for this 3-days event. This event provided an amalgamation of six prominent speakers and all participants whose interests lay mainly in applying MS-based and non-MS-based proteomics for clinical investigation.

Asia-Oceania HUPO: Past, Present, and Future.

The Asia-Oceania Human Proteome Organization (AOHUPO; www.aohupo.org) was officially founded on June 7, 2001, by Richard J. Simpson (Australia), Akira Tsugita (Japan), and Young-Ki Paik (Korea) and launched on October 1-4, 2001, at the second scientific meeting of the International Proteomics Conference held in Canberra, Australia. Inaugural council members of the AOHUPO elected were Richard J. Simpson (Australia, president), Qi-Chang Xia (China), Kazuyuki Nakamura (Japan), Akira Tsugita (Japan, VIce President), Young-Ki Paik (Korea, secretary general), Mike Hubbard (New Zealand), Max C. M. Chung (Singapore), Shui-Tien Chen (Taiwan), and John Bennett (Philippines). The first AOHUPO conference was held on March 26-27, 2002, at the Seoul National University, Seoul, Korea, conjointly with the second Annual Meeting of KHUPO. Since then, biennial AOHUPO conferences have been held in Taipei (2004), Singapore (2006), Cairns (2008), Hyderabad (2010), Beijing (2012), Bangkok (2014), Sun Moon Lake (2016), and Osaka (2018). The 10th AOHUPO conference is scheduled to be held in Busan on June 30 to July 2, 2021, to celebrate our 20th anniversary.

Spatially Resolved Proteomic and Transcriptomic Profiling of Anaplastic Lymphoma Kinase-Rearranged Pulmonary Adenocarcinomas Reveals Key Players in Inter- and Intratumoral Heterogeneity.

Pulmonary adenocarcinomas (pADCs) with an ALK rearrangement are a rare cancer subtype, necessitating comprehensive molecular investigations to unravel their heterogeneity and improve therapeutic strategies. In this pilot study, we employed spatial transcriptomic (NanoString GeoMx) and proteomic profiling to investigate seven treatment-naïve pADCs with an ALK rearrangement. On each FFPE tumor slide, 12 smaller and 2-6 larger histopathologically annotated regions were selected for transcriptomic and proteomic analysis, respectively. The correlation between proteomics and transcriptomics was modest (average Pearson's r = 0.43 at the gene level). Intertumoral heterogeneity was more pronounced than intratumoral heterogeneity, and normal adjacent tissue exhibited distinct molecular characteristics. We identified potential markers and dysregulated pathways associated with tumors, with a varying extent of immune infiltration, as well as with mucin and stroma content. Notably, some markers appeared to be specific to the ALK-driven subset of pADCs. Our data showed that within tumors, elements of the extracellular matrix, including FN1, exhibited substantial variability. Additionally, we mapped the co-localization patterns of tumor microenvironment elements. This study represents the first spatially resolved profiling of ALK-driven pADCs at both the gene and protein expression levels. Our findings may contribute to a better understanding of this cancer type prior to treatment with ALK inhibitors.

A natural small molecule induces MAPT clearance via mTOR-independent autophagy.

Autophagy, the process of lysosomal degradation of biological materials within cells, is often halted abnormally in proteopathies, such as tauopathy and amyloidopathy. Thus, autophagy regulators that rescue dysregulated autophagy have great potential to treat proteopathies. We previously reported that the natural small molecule kaempferide (Kaem) induces autophagy without perturbing mTOR signaling. Here, we report that Kaem promotes lysosomal degradation of microtubule-associated protein tau (MAPT) in inducible MAPT cells. Kaem enhanced autophagy flux by mitigating microtubule-associated protein 1 light chain 3 (LC3) accumulation when MAPT expression was induced. Kaem also promoted activation of transcription factor EB (TFEB) without inhibiting mTOR and without mTOR inhibition-mediated cytotoxicity. In addition, Kaem-induced MAPT degradation was abolished in the absence of mitochondrial elongation factor Tu (TUFM), which was previously shown to be a direct binding partner of Kaem. Collectively, these results demonstrate that Kaem could be a potential therapeutic for tauopathy and reveal that TUFM can be a drug target for autophagy-driven disorders.

Functional inhibition of fatty acid binding protein 4 ameliorates impaired ciliogenesis in GCs.

Ciliogenesis is often impaired in some cancer cells, leading to acceleration of cancer phenotypes such as cell migration and proliferation. From the investigation of primary cilia of 16 gastric cancer cells (GCs), we found that GCs could be grouped into four primary cilia (PC)-positive GCs and 12 PC-negative GCs. The proliferation of the PC-positive GCs was lower than that of PC-negative GCs. To explore the role of fatty acid binding protein 4 (FABP4), which is a known oncogenic factor, in ciliogenesis, FABP4 expression and function were inhibited by transfection of cells with short interfering RNA targeting FABP4 (siFABP4) or FABP4 inhibitor treatment. Notably, the proliferation and migration of the cilia-forming GCs was effectively suppressed by inhibition of FABP4. In addition, the primary cilia in GCs were restored by a factor greater than two, suggesting a negative role of FABP4 in ciliogenesis in these GCs and FABP4 as a potential anticancer target.

Enhanced production of clavulanic acid by improving glycerol utilization using reporter-guided mutagenesis of an industrial Streptomyces clavuligerus strain.

Clavulanic acid (CA) produced by Streptomyces clavuligerus is a clinically important ß-lactamase inhibitor. It is known that glycerol utilization can significantly improve cell growth and CA production of S. clavuligerus. We found that the industrial CA-producing S. clavuligerus strain OR generated by random mutagenesis consumes less glycerol than the wild-type strain; we then developed a mutant strain in which the glycerol utilization operon is overexpressed, as compared to the parent OR strain, through iterative random mutagenesis and reporter-guided selection. The CA production of the resulting S. clavuligerus ORUN strain was increased by approximately 31.3% (5.21 ± 0.26 g/l) in a flask culture and 17.4% (6.11 ± 0.36 g/l) in a fermenter culture, as compared to that of the starting OR strain. These results confirmed the important role of glycerol utilization in CA production and demonstrated that reporter-guided mutant selection is an efficient method for further improvement of randomly mutagenized industrial strains.

Profiling the Protein Targets of Unmodified Bio-Active Molecules with Drug Affinity Responsive Target Stability and Liquid Chromatography/Tandem Mass Spectrometry.

Identifying the target proteins of bioactive small molecules is a key step in understanding mode-of-action of the drug and addressing the underlying mechanisms responsible for a particular phenotype. Proteomics has been successfully used to elucidate the target protein profiles of unmodified and ligand-modified bioactive small molecules. In the latter approach, compounds can be modified via click chemistry and combined with activity-based protein profiling. Target proteins are then enriched by performing a pull-down with the modified ligand. Methods that utilize unmodified bioactive small molecules include the cellular thermal shift assay, thermal proteome profiling, stability of proteins from rates of oxidation, and the drug affinity responsive target stability (DARTS) determination (or read-out). This review highlights recent proteomic approaches utilizing data-dependent analysis and data-independent analysis to identify target proteins by DARTS. When combined with liquid chromatography/tandem mass spectrometry, DARTS enables the identification of proteins that bind to drug molecules that leads to a conformational change in the target protein(s). In addition, an effective strategy is proposed for selecting the target protein(s) from within the pool of analyzed candidates. With additional complementary methods, the biologically relevant target proteins that bind to the small bio-active molecules can be further validated.

Novel functional proteins coded by the human genome discovered in metastases of melanoma patients.

In the advanced stages, malignant melanoma (MM) has a very poor prognosis. Due to tremendous efforts in cancer research over the last 10 years, and the introduction of novel therapies such as targeted therapies and immunomodulators, the rather dark horizon of the median survival has dramatically changed from under 1 year to several years. With the advent of proteomics, deep-mining studies can reach low-abundant expression levels. The complexity of the proteome, however, still surpasses the dynamic range capabilities of current analytical techniques. Consequently, many predicted protein products with potential biological functions have not yet been verified in experimental proteomic data. This category of 'missing proteins' (MP) is comprised of all proteins that have been predicted but are currently unverified. As part of the initiative launched in 2016 in the USA, the European Cancer Moonshot Center has performed numerous deep proteomics analyses on samples from MM patients. In this study, nine MPs were clearly identified by mass spectrometry in MM metastases. Some MPs significantly correlated with proteins that possess identical PFAM structural domains; and other MPs were significantly associated with cancer-related proteins. This is the first study to our knowledge, where unknown and novel proteins have been annotated in metastatic melanoma tumour tissue.

Design, synthesis, and biological evaluation of novel pyrrolo[1,2-a]pyrazine derivatives.

A pyrrolo[1,2-a]pyrazine-based chemical territory was expanded via construction of new chemical library with distinctive substitution patterns, which was made possible by regiodivergent electrophilic acylation followed by aldol condensation. Biological screening of the compounds in this class revealed that the viability of human lymphoma U937 cells was strongly inhibited by 6b with a methoxy group at the o-position of the aromatic ring, but not by compounds 6t-w bearing a halogen at the o-position. Furthermore, 6x having a 2,4-dimethoxyphenyl group inhibited the survival of U937 cells more potently than 6b. In contrast, 6y possessing a 2,5-dimethoxyphenyl moiety did not show effective inhibition, implying the importance of orientation of the substituent(s) around the benzene ring. The anticancer action of 6x with safe therapeutic window could be associated with the FTase-p38 signaling axis.

Clinical protein science in translational medicine targeting malignant melanoma.

Melanoma of the skin is the sixth most common type of cancer in Europe and accounts for 3.4% of all diagnosed cancers. More alarming is the degree of recurrence that occurs with approximately 20% of patients lethally relapsing following treatment. Malignant melanoma is a highly aggressive skin cancer and metastases rapidly extend to the regional lymph nodes (stage 3) and to distal organs (stage 4). Targeted oncotherapy is one of the standard treatment for progressive stage 4 melanoma, and BRAF inhibitors (e.g. vemurafenib, dabrafenib) combined with MEK inhibitor (e.g. trametinib) can effectively counter BRAFV600E-mutated melanomas. Compared to conventional chemotherapy, targeted BRAFV600E inhibition achieves a significantly higher response rate. After a period of cancer control, however, most responsive patients develop resistance to the therapy and lethal progression. The many underlying factors potentially causing resistance to BRAF inhibitors have been extensively studied. Nevertheless, the remaining unsolved clinical questions necessitate alternative research approaches to address the molecular mechanisms underlying metastatic and treatment-resistant melanoma. In broader terms, proteomics can address clinical questions far beyond the reach of genomics, by measuring, i.e. the relative abundance of protein products, post-translational modifications (PTMs), protein localisation, turnover, protein interactions and protein function. More specifically, proteomic analysis of body fluids and tissues in a given medical and clinical setting can aid in the identification of cancer biomarkers and novel therapeutic targets. Achieving this goal requires the development of a robust and reproducible clinical proteomic platform that encompasses automated biobanking of patient samples, tissue sectioning and histological examination, efficient protein extraction, enzymatic digestion, mass spectrometry-based quantitative protein analysis by label-free or labelling technologies and/or enrichment of peptides with specific PTMs. By combining data from, e.g. phosphoproteomics and acetylomics, the protein expression profiles of different melanoma stages can provide a solid framework for understanding the biology and progression of the disease. When complemented by proteogenomics, customised protein sequence databases generated from patient-specific genomic and transcriptomic data aid in interpreting clinical proteomic biomarker data to provide a deeper and more comprehensive molecular characterisation of cellular functions underlying disease progression. In parallel to a streamlined, patient-centric, clinical proteomic pipeline, mass spectrometry-based imaging can aid in interrogating the spatial distribution of drugs and drug metabolites within tissues at single-cell resolution. These developments are an important advancement in studying drug action and efficacy in vivo and will aid in the development of more effective and safer strategies for the treatment of melanoma. A collaborative effort of gargantuan proportions between academia and healthcare professionals has led to the initiation, establishment and development of a cutting-edge cancer research centre with a specialisation in melanoma and lung cancer. The primary research focus of the European Cancer Moonshot Lund Center is to understand the impact that drugs have on cancer at an individualised and personalised level. Simultaneously, the centre increases awareness of the relentless battle against cancer and attracts global interest in the exceptional research performed at the centre.

Improved production of clavulanic acid by reverse engineering and overexpression of the regulatory genes in an industrial Streptomyces clavuligerus strain.

Genomic analysis of the clavulanic acid (CA)-high-producing Streptomyces clavuligerus strains, OL13 and OR, developed through random mutagenesis revealed a frameshift mutation in the cas1 gene-encoding clavaminate synthase 1. Overexpression of the intact cas1 in S. clavuligerus OR enhanced the CA titer by approximately 25%, producing ~ 4.95 g/L of CA, over the OR strain in the flask culture. Moreover, overexpression of the pathway-specific positive regulatory genes, ccaR and claR, in the OR strain improved CA yield by approximately 43% (~ 5.66 g/L) in the flask. However, co-expression of the intact cas1 with ccaR-claR did not further improve CA production. In the 7 L fermenter culture, maximum CA production by the OR strain expressing the wild-type cas1 and ccaR-claR reached approximately 5.52 g/L and 6.01 g/L, respectively, demonstrating that reverse engineering or simple rational metabolic engineering is an efficient method for further improvement of industrial strains.

FK506, an Immunosuppressive Drug, Induces Autophagy by Binding to the V-ATPase Catalytic Subunit A in Neuronal Cells.

The drug FK506 (tacrolimus, fujimycin) exerts its immunosuppressive effects by regulating the nuclear factor of the activated T-cell (NFAT) family of transcription factors. However, FK506 also exhibits neuroprotective effects, but its direct target proteins that mediate these effects have not been determined. To identify the target proteins responsible for FK506's neuroprotective effects, the drug affinity responsive target stability (DARTS) method was performed using label-free FK506, and LC-MS/MS analysis of the FK506-treated proteome was also performed. Using DARTS and LC-MS/MS analyses in combination with reference studies, V-ATPase catalytic subunit A (ATP6V1A) was identified as a new target protein of FK506. The biological relevance of ATP6V1A in mediating the neuroprotective effects of FK506 was validated by analyzing FK506 activity with respect to autophagy via acridine orange staining and transcription factor EB (TFEB) translocation assay. These analyses demonstrated that the binding of FK506 with ATP6V1A induces autophagy by activating the translocation of TFEB from the cytosol into the nucleus. Because autophagy has been identified as a mechanism for treating neurodegenerative diseases and because we have demonstrated that FK506 induces autophagy, this study demonstrates that FK506 is a possible new therapy for treating neurodegenerative diseases.

The effect of indatraline on angiogenesis suppression through HIF-1α-mediated VEGF inhibition.

The present research reports a novel biological activity of indatraline, a compound clinically used as an antidepressant. We previously identified indatraline as an autophagy inducer. Autophagy is an intracellular catabolic pathway for degrading or recycling unnecessary organelles in response to cellular stress. Indatraline-mediated autophagy induction results from mTOR inhibition. The mTOR is a negative regulator of autophagy as well as a master regulator of angiogenesis. Angiogenesis defines the process by which new vessels are formed from pre-existing vascular tissues, providing nutrients to cancer cells, allowing rapid tumor progression. Accordingly, targeting angiogenesis to prevent cancer is an attractive therapeutic strategy. Here, we demonstrate that indatraline possibly acts to suppress tumor-mediated angiogenesis via downregulation of HIF-1α-mediated VEGF expression. The effects of indatraline on autophagy and angiogenesis could make it a potential drug candidate toward cancer treatment.

Inhibition of 5-lipoxygenase suppresses vascular endothelial growth factor-induced angiogenesis in endothelial cells.

5-Lipoxygenase (5-LOX) is an enzyme that converts arachidonic acid from the cell membrane into leukotriene, a signal lipid mediator. 5-LOX deficiency markedly attenuates the formation of aneurysms in knockout mice. In addition, Zileuton, a clinical drug targeting 5-LOX, is used for treatment of asthma. However, it is unclear whether 5-LOX inhibition results in anti-angiogenic effects for applications in cancer therapy. To explore the roles of 5-LOX in angiogenesis and its potential as a therapeutic target in cancer, the effects of a newly synthesized 5-LOX inhibitor, F3, on in vitro and in vivo angiogenesis were investigated. The results showed that 5-LOX inhibition by F3 suppressed in vitro vascular endothelial growth factor (VEGF)-induced tube formation and chemo-invasion of endothelial cells (ECs). 5-LOX inhibition also decreased VEGF-induced extracellular signal-regulated kinase (ERK) phosphorylation in ECs. Notably, 5-LOX knockdown phenocopied the anti-angiogenic activity of the 5-LOX inhibitor F3 in a concentration-dependent manner. F3 did not affect the activities of VEGF receptor 2 or AKT. In vivo, the compound significantly inhibited the formation of the chorioallantoic membrane at nontoxic doses. These results demonstrated that 5-LOX played an important role in angiogenesis and that its inhibitor F3 could be a new anti-angiogenic agent targeting VEGF signaling.

Daptomycin, a last-resort antibiotic, binds ribosomal protein S19 in humans.

BACKGROUND: Daptomycin is a recently introduced, last-resort antibiotic that displays a unique mode of action against Gram-positive bacteria that is not fully understood. Several bacterial targets have been proposed but no human binding partner is known. METHODS: In the present study we tested daptomycin in cell viability and proliferation assays against six human cell lines, describe the synthesis of biotinylated and fluorescently labeled analogues of daptomycin. Biotinylated daptomycin was used as bait to isolate the human binding partner by the application of reverse chemical proteomics using T7 phage display of five human tumor cDNA libraries. The interaction between the rescued protein and daptomycin was validated via siRNA knockdown, DARTS assay and immunocytochemistry. RESULTS: We have found that daptomycin possesses selective growth inhibition of some cancer cell lines, especially MCF7. The unbiased interrogation of human cDNA libraries, displayed on bacteriophage T7, revealed a single human target of daptomycin; ribosomal protein S19. Using a drug affinity responsive target stability (DARTS) assay in vitro, we show that daptomycin stabilizes RPS19 toward pronase. Fluorescently labeled daptomycin stained specific structures in HeLa cells and co-localized with a RPS19 antibody. CONCLUSION: This study provides, for the first time, a human protein target of daptomycin and identifies RPS19 as a possible anticancer drug target for the development of new pharmacological applications and research.

Discovery of novel drug targets and their functions using phenotypic screening of natural products.

Natural products are valuable resources that provide a variety of bioactive compounds and natural pharmacophores in modern drug discovery. Discovery of biologically active natural products and unraveling their target proteins to understand their mode of action have always been critical hurdles for their development into clinical drugs. For effective discovery and development of bioactive natural products into novel therapeutic drugs, comprehensive screening and identification of target proteins are indispensable. In this review, a systematic approach to understanding the mode of action of natural products isolated using phenotypic screening involving chemical proteomics-based target identification is introduced. This review highlights three natural products recently discovered via phenotypic screening, namely glucopiericidin A, ecumicin, and terpestacin, as representative case studies to revisit the pivotal role of natural products as powerful tools in discovering the novel functions and druggability of targets in biological systems and pathological diseases of interest.

Turmeric extract and its active compound, curcumin, protect against chronic CCl4-induced liver damage by enhancing antioxidation.

BACKGROUND: Curcumin, a major active component of turmeric, has previously been reported to alleviate liver damage. Here, we investigated the mechanism by which turmeric and curcumin protect the liver against carbon tetrachloride (CCl4)-induced injury in rats. We hypothesized that turmeric extract and curcumin protect the liver from CCl4-induced liver injury by reducing oxidative stress, inhibiting lipid peroxidation, and increasing glutathione peroxidase activation. METHODS: Chronic hepatic stress was induced by a single intraperitoneal injection of CCl4 (0.1 ml/kg body weight) into rats. Turmeric extracts and curcumin were administered once a day for 4 weeks at three dose levels (100, 200, and 300 mg/kg/day). We performed ALT and AST also measured of total lipid, triglyceride, cholesterol levels, and lipid peroxidation. RESULT: We found that turmeric extract and curcumin significantly protect against liver injury by decreasing the activities of serum aspartate aminotransferase and alanine aminotransferase and by improving the hepatic glutathione content, leading to a reduced level of lipid peroxidase. CONCLUSIONS: Our data suggest that turmeric extract and curcumin protect the liver from chronic CCl4-induced injury in rats by suppressing hepatic oxidative stress. Therefore, turmeric extract and curcumin are potential therapeutic antioxidant agents for the treatment of hepatic disease.

HIF-1α suppressing small molecule, LW6, inhibits cancer cell growth by binding to calcineurin b homologous protein 1.

Hypoxia inducible factor-1 alpha (HIF-1α) plays an important role in angiogenesis and metastasis and is a promising therapeutic target for the development of anti-cancer drugs. We recently developed a new synthetic small molecule inhibitor of HIF-1α, LW6, which results in inhibition of angiogenesis. To investigate its underlying mechanism, target protein identification was conducted by reverse chemical proteomics using phage display. We identified calcineurin b homologous protein 1 (CHP1) as a target protein of LW6, which specifically binds to CHP1 in a Ca(2+) dependent manner. Covalent labeling of LW6 using photoaffinity and click chemistry demonstrated its co-localization with CHP1 in live cells. HIF-1α was decreased by CHP1 knockdown in HepG2 cells, and angiogenesis was not induced in HUVEC cells by treatment with conditioned media from CHP1 knockdown cells compared to the control. These data demonstrated that LW6 inhibited HIF-1α stability via direct binding with CHP1 resulting in suppression of angiogenesis, providing a new insight into the role of CHP1 in HIF-1α regulation. LW6 could serve as a new chemical probe to explore CHP1 function.