A novel frameshift variant of LMX1A that leads to autosomal dominant non-syndromic sensorineural hearing loss: functional characterization of the C-terminal domain in LMX1A.

Non-syndromic sensorineural hearing loss (NSHL) is a group of genetically heterogeneous conditions with broad phenotypic heterogeneity. There is, at present, no curative treatment for genetic hearing loss (HL). Early molecular diagnosis of progressive disorders and elucidation of the causes and pathomechanisms are essential for developing therapeutic strategies. Here, we identified a novel rare frameshift variant of LMX1A (c.915dup), which resulted in the C-terminal-altered and -truncated LMX1A (p.Val306Cysfs*32). This C-terminal frameshift mutation co-segregated with autosomal dominant (AD) NSHL in a four-generation Chinese family, suggesting that the LMX1A non-missense mutation is also contributed to ADNSHL. In this family, the affected individuals exhibited the variable auditory phenotypes ranging from profound congenital deafness at birth or to mild/moderate HL in adulthood. We also found that the embryonic cells carrying with the heterozygous variant significantly expressed several upregulated HL-associated genes at transcriptional level. In vitro splicing assay suggested that the LMX1A mRNA with c.915dup did not cause nonsense-mediated decay and was translated into a truncated LMX1A. In addition, electrophoresis mobility shift assay and luciferase assays have shown that the highly conserved C-terminal domain (amino acid 306-382) of the LMX1A was required for regulating the protein-DNA interaction and transactivation in vitro. Furthermore, apoptosis assays suggested that the C-terminal domain of the LMX1A was important for mediating apoptosis in the cochlear hair cells. Our work provided the multiline of the evidence to support that non-missense mutation of LMX1A leads to ADNSHL and the C-terminal domain of LMX1A is important for mediating transcriptional activity and associated with promoting apoptosis in the cells.

Protein Kinase D3 promotes the cell proliferation by activating the ERK1/c-MYC axis in breast cancer.

Breast cancer is the second leading death cause of cancer death for all women. Previous study suggested that Protein Kinase D3 (PRKD3) was involved in breast cancer progression. In addition, the protein level of PRKD3 in triple-negative breast adenocarcinoma was higher than that in normal breast tissue. However, the oncogenic mechanisms of PRKD3 in breast cancer is not fully investigated. Multi-omic data showed that ERK1/c-MYC axis was identified as a major pivot in PRKD3-mediated downstream pathways. Our study provided the evidence to support that the PRKD3/ERK1/c-MYC pathway play an important role in breast cancer progression. We found that knocking out PRKD3 by performing CRISPR/Cas9 genome engineering technology suppressed phosphorylation of both ERK1 and c-MYC but did not down-regulate ERK1/2 expression or phosphorylation of ERK2. The inhibition of ERK1 and c-MYC phosphorylation further led to the lower protein level of c-MYC and then reduced the expression of the c-MYC target genes in breast cancer cells. We also found that loss of PRKD3 reduced the rate of the cell proliferation in vitro and tumour growth in vivo, whereas ectopic (over)expression of PRKD3, ERK1 or c-MYC in the PRKD3-knockout breast cells reverse the suppression of the cell proliferation and tumour growth. Collectively, our data strongly suggested that PRKD3 likely promote the cell proliferation in the breast cancer cells by activating ERK1-c-MYC axis.

Structure of the Z Ring-associated Protein, ZapD, Bound to the C-terminal Domain of the Tubulin-like Protein, FtsZ, Suggests Mechanism of Z Ring Stabilization through FtsZ Cross-linking.

Cell division in most bacteria is mediated by the tubulin-like FtsZ protein, which polymerizes in a GTP-dependent manner to form the cytokinetic Z ring. A diverse repertoire of FtsZ-binding proteins affects FtsZ localization and polymerization to ensure correct Z ring formation. Many of these proteins bind the C-terminal domain (CTD) of FtsZ, which serves as a hub for FtsZ regulation. FtsZ ring-associated proteins, ZapA-D (Zaps), are important FtsZ regulatory proteins that stabilize FtsZ assembly and enhance Z ring formation by increasing lateral assembly of FtsZ protofilaments, which then form the Z ring. There are no structures of a Zap protein bound to FtsZ; therefore, how these proteins affect FtsZ polymerization has been unclear. Recent data showed ZapD binds specifically to the FtsZ CTD. Thus, to obtain insight into the ZapD-CTD interaction and how it may mediate FtsZ protofilament assembly, we determined the Escherichia coli ZapD-FtsZ CTD structure to 2.67 Å resolution. The structure shows that the CTD docks within a hydrophobic cleft in the ZapD helical domain and adopts an unusual structure composed of two turns of helix separated by a proline kink. FtsZ CTD residue Phe-377 inserts into the ZapD pocket, anchoring the CTD in place and permitting hydrophobic contacts between FtsZ residues Ile-374, Pro-375, and Leu-378 with ZapD residues Leu-74, Trp-77, Leu-91, and Leu-174. The structural findings were supported by mutagenesis coupled with biochemical and in vivo studies. The combined data suggest that ZapD acts as a molecular cross-linking reagent between FtsZ protofilaments to enhance FtsZ assembly.

Structural and Functional Analyses Reveal Insights into the Molecular Properties of the Escherichia coli Z Ring Stabilizing Protein, ZapC.

In Escherichia coli cell division is driven by the tubulin-like GTPase, FtsZ, which forms the cytokinetic Z-ring. The Z-ring serves as a dynamic platform for the assembly of the multiprotein divisome, which catalyzes membrane cleavage to create equal daughter cells. Several proteins effect FtsZ assembly, thereby providing spatiotemporal control over cell division. One important class of FtsZ interacting/regulatory proteins is the Z-ring-associated proteins, Zaps, which typically modulate Z-ring formation by increasing lateral interactions between FtsZ protofilaments. Strikingly, these Zap proteins show no discernable sequence similarity, suggesting that they likely harbor distinct structures and mechanisms. The 19.8-kDa ZapC in particular shows no homology to any known protein. To gain insight into ZapC function, we determined its structure to 2.15 Å and performed genetic and biochemical studies. ZapC is a monomer composed of two domains, an N-terminal α/ß region and a C-terminal twisted ß barrel-like domain. The structure contains two pockets, one on each domain. The N-domain pocket is lined with residues previously implicated to be important for ZapC function as an FtsZ bundler. The adjacent C-domain pocket contains a hydrophobic center surrounded by conserved basic residues. Mutagenesis analyses indicate that this pocket is critical for FtsZ binding. An extensive FtsZ binding surface is consistent with the fact that, unlike many FtsZ regulators, ZapC binds the large FtsZ globular core rather than C-terminal tail, and the presence of two adjacent pockets suggests possible mechanisms for ZapC-mediated FtsZ bundling.

FtsZ ring stability: of bundles, tubules, crosslinks, and curves.

The first step in bacterial cytokinesis is the assembly of a stable but dynamic cytokinetic ring made up of the essential tubulin homolog FtsZ at the future site of division. Although FtsZ and its role in cytokinesis have been studied extensively, the precise architecture of the in vivo medial FtsZ ring (Z ring) is not well understood. Recent advances in superresolution imaging suggest that the Z ring comprises short, discontinuous, and loosely bundled FtsZ polymers, some of which are tethered to the membrane. A diverse array of regulatory proteins modulate the assembly, stability, and disassembly of the Z ring via direct interactions with FtsZ. Negative regulators of FtsZ play a critical role in ensuring the accurate positioning of FtsZ at the future site of division and in maintaining Z ring dynamics by controlling FtsZ polymer assembly/disassembly processes. Positive regulators of FtsZ are essential for tethering FtsZ polymers to the membrane and promoting the formation of stabilizing lateral interactions, permitting assembly of a mature Z ring. The past decade has seen the identification of several factors that promote FtsZ assembly, presumably through a variety of distinct molecular mechanisms. While a few of these proteins are broadly conserved, many positive regulators of FtsZ assembly are limited to small groups of closely related organisms, suggesting that FtsZ assembly is differentially modulated across bacterial species. In this review, we focus on the roles of positive regulators in Z ring assembly and in maintaining the integrity of the cytokinetic ring during the early stages of division.

Targeting epidermal growth factor-overexpressing triple-negative breast cancer by natural killer cells expressing a specific chimeric antigen receptor.

OBJECTIVES: Traditional cancer therapy and regular immunotherapy are ineffective for treating triple-negative breast cancer (TNBC) patients. Recently, chimeric antigen receptor-engineered natural killer cells (CAR NK) have been applied to target several hormone receptors on different cancer cells to improve the efficacy of immunotherapy. Furthermore, epidermal growth factor receptor (EGFR) is a potential therapeutic target for TNBC. Here, we demonstrated that EGFR-specific CAR NK cells (EGFR-CAR NK cells) could be potentially used to treat patients with TNBC exhibiting enhanced EGFR expression. MATERIALS AND METHODS: We investigated the cytotoxic effects of EGFR-CAR NK cells against TNBC cells in vitro and in vivo. The two types of EGFR-CAR NK cells were generated by transducing lentiviral vectors containing DNA sequences encoding the single-chain variable fragment (scFv) regions of the two anti-EGFR antibodies. The cytotoxic and anti-tumor effects of the two cell types were examined by performing cytokine release and cytotoxicity assays in vitro, and tumor growth assays in breast cancer cell line-derived xenograft (CLDX) and patient-derived xenograft (PDX) mouse models. RESULTS: Both EGFR-CAR NK cell types were activated by TNBC cells exhibiting upregulated EGFR expression and specifically triggered the lysis of the TNBC cells in vitro. Furthermore, the two EGFR-CAR NK cell types inhibited CLDX and PDX tumors in mice. CONCLUSIONS: This study suggested that treatment with EGFR-CAR NK cells could be a promising strategy for TNBC patients.

EGFR-specific CAR-T cells trigger cell lysis in EGFR-positive TNBC.

Triple-negative breast cancer (TNBC) is an aggressive cancer subtype for which effective therapies are lacking. Epidermal growth factor receptor (EGFR) is overexpressed in various types of TNBC cells, and several EGFR-specific immunotherapies have been used to treat cancer patients. Chimeric antigen receptor engineered T (CAR-T) cells have also been used as cancer therapies. In this study, we generated two types of EGFR-specific CAR-modified T cells using lentiviral vectors with DNA sequences encoding the scFv regions of two anti-EGFR antibodies. The cytotoxic and antitumor effects of these CAR-modified T cells were examined in cytokine release and cytotoxicity assays in vitro and in tumor growth assays in TNBC cell line- and patient-derived xenograft mouse models. Both types of EGFR-specific CAR-T cells were activated by high-EGFR-expressing TNBC cells and specifically triggered TNBC cell lysis in vitro. Additionally, the CAR-T cells inhibited growth of cell-line- and patient-derived xenograft TNBC tumors in mice. These results suggest that EGFR-specific CAR-T cells might be a promising therapeutic strategy in patients with high-EGFR-expressing TNBC.

Phosphorylation at Ser473 regulates heterochromatin protein 1 binding and corepressor function of TIF1beta/KAP1.

BACKGROUND: As an epigenetic regulator, the transcriptional intermediary factor 1beta (TIF1beta)/KAP1/TRIM28) has been linked to gene expression and chromatin remodeling at specific loci by association with members of the heterochromatin protein 1 (HP1) family and various other chromatin factors. The interaction between TIF1beta and HP1 is crucial for heterochromatin formation and maintenance. The HP1-box, PXVXL, of TIF1beta is responsible for its interaction with HP1. However, the underlying mechanism of how the interaction is regulated remains poorly understood. RESULTS: This work demonstrates that TIF1beta is phosphorylated on Ser473, the alteration of which is dynamically associated with cell cycle progression and functionally linked to transcriptional regulation. Phosphorylation of TIF1beta/Ser473 coincides with the induction of cell cycle gene cyclin A2 at the S-phase. Interestingly, chromatin immunoprecipitation demonstrated that the promoter of cyclin A2 gene is occupied by TIF1beta and that such occupancy is inversely correlated with Ser473 phosphorylation. Additionally, when HP1beta was co-expressed with TIF1beta/S473A, but not TIF1beta/S473E, the colocalization of TIF1beta/S473A and HP1beta to the promoters of Cdc2 and Cdc25A was enhanced. Non-phosphorylated TIF1beta/Ser473 allowed greater TIF1beta association with the regulatory regions and the consequent repression of these genes. Consistent with possible inhibition of TIF1beta's corepressor function, the phosphorylation of the Ser473 residue, which is located near the HP1-interacting PXVXL motif, compromised the formation of TIF1beta-HP1 complex. Finally, we found that the phosphorylation of TIF1beta/Ser473 is mediated by the PKCdelta pathway and is closely linked to cell proliferation. CONCLUSION: The modulation of HP1beta-TIF1beta interaction through the phosphorylation/de-phosphorylation of TIF1beta/Ser473 may constitute a molecular switch that regulates the expression of particular genes. Higher levels of phosphorylated TIF1beta/Ser473 may be associated with the expression of key regulatory genes for cell cycle progression and the proliferation of cells.

Long non-coding RNA MYU promotes prostate cancer proliferation by mediating the miR-184/c-Myc axis.

Long non-coding RNAs (lncRNAs) play critical roles in tumorigenesis and cancer progression. The c-Myc upregulated lncRNA MYU (VPS9D1 antisense RNA1, annotated as VPS9D1-AS1) has been reported in several common types of human cancers, which has revealed that lncRNA MYU could function as either an oncogene or a tumor-suppressor gene in different cancer types. However, the function of lncRNA MYU in prostate cancer remains unknown. In the present study, we demonstrated that lncRNA MYU is significantly upregulated in prostate cancer tissues. MYU knockdown impaired prostate cancer cell growth and migration as shown from cell viability, colony formation, Transwell and wound healing assays. In contrast, MYU overexpression displayed opposite effects. No correlation was noted between MYU and its cognate VPS9D1 expression level. Moreover, lncRNA MYU did not regulate the expression of VPS9D1 either at the mRNA or protein level as detected using qRT-PCR and western blotting assays. Furthermore, lncRNA MYU was able to be transported into the extracellular milieu by means of exosomes, and then promoted adjacent cell proliferation and migration. Mechanistically, lncRNA MYU upregulated c-Myc by competitively binding miR-184 and then induced the proliferation of prostate cancer. Thus, this study demonstrated that lncRNA MYU functions as an oncogene in prostate cancer at least in part through the miR-184/c-Myc axis, and may serve as a potential diagnostic biomarker and therapeutic target.

Characterization of the FtsZ C-Terminal Variable (CTV) Region in Z-Ring Assembly and Interaction with the Z-Ring Stabilizer ZapD in E. coli Cytokinesis.

Polymerization of a ring-like cytoskeletal structure, the Z-ring, at midcell is a highly conserved feature in virtually all bacteria. The Z-ring is composed of short protofilaments of the tubulin homolog FtsZ, randomly arranged and held together through lateral interactions. In vitro, lateral associations between FtsZ protofilaments are stabilized by crowding agents, high concentrations of divalent cations, or in some cases, low pH. In vivo, the last 4-10 amino acid residues at the C-terminus of FtsZ (the C-terminal variable region, CTV) have been implicated in mediating lateral associations between FtsZ protofilaments through charge shielding. Multiple Z-ring associated proteins (Zaps), also promote lateral interactions between FtsZ protofilaments to stabilize the FtsZ ring in vivo. Here we characterize the complementary role/s of the CTV of E. coli FtsZ and the FtsZ-ring stabilizing protein ZapD, in FtsZ assembly. We show that the net charge of the FtsZ CTV not only affects FtsZ protofilament bundling, confirming earlier observations, but likely also the length of the FtsZ protofilaments in vitro. The CTV residues also have important consequences for Z-ring assembly and interaction with ZapD in the cell. ZapD requires the FtsZ CTV region for interaction with FtsZ in vitro and for localization to midcell in vivo. Our data suggest a mechanism in which the CTV residues, particularly K380, facilitate a conformation for the conserved carboxy-terminal residues in FtsZ, that lie immediately N-terminal to the CTV, to enable optimal contact with ZapD. Further, phylogenetic analyses suggest a correlation between the nature of FtsZ CTV residues and the presence of ZapD in the ß- γ-proteobacterial species.

Differential activation of a C/EBP beta isoform by a novel redox switch may confer the lipopolysaccharide-inducible expression of interleukin-6 gene.

C/EBP beta, a member of the CCAAT/enhancer binding protein (C/EBP) family, is one of the key transcription factors responsible for the induction of a wide array of genes, some of which play important roles in innate immunity, inflammatory response, adipocyte and myeloid cell differentiation, and the acute phase response. Three C/EBP beta isoforms (i.e. LAP*, LAP, and LIP) were known to arise from differential translation initiation and display different functions in gene regulation. C/EBP beta is known to induce interleukin (IL)-6 gene when P388D1 cells are treated with lipopolysaccharide (LPS). Exactly how the transcriptional activities of C/EBP beta isoforms are involved in the regulation of the IL-6 gene remains unclear. Here we report that LPS-induced expression of IL-6 gene in P388D1 cells is mediated by a redox switch-activated LAP*. The intramolecular disulfide bonds of LAP* and LAP have been determined. Among the cysteine residues, amino acid 11 (Cys11) of LAP* plays key roles for determining the overall intramolecular disulfide bonds that form the basis for redox switch regulation. The DNA binding activity and transcriptional activity of LAP* are enhanced under reducing condition. LAP and LIP, lacking 21 and 151 amino acids, respectively, in the N-terminal region, are not regulated in a similar redox-responsive manner. Our results indicate that LAP* is the primary isoform of C/EBP beta that regulates, through a redox switch, the LPS-induced expression of the IL-6 gene.