High yield expression of biologically active recombinant full length human tuftelin protein in baculovirus-infected insect cells

Tuftelin's involvement in embryonic development

Little is known about tuftelin expression in the developing embryo, previously it was thought to play a role in tooth enamel mineralization. In this study we show tuftelin's spatio-temporal expression in mineralizing and nonmineralizing tissues of the craniofacial complex in the developing mouse embryo. Embryos aged E10.5-E18.5 and newborns aged P3 were used in this study. Polymerase chain reaction (PCR), Real-time PCR, sequencing, and in-situ hybridization were used to detect and quantify messenger RNA (mRNA) expression in different developmental stages. We applied indirect immunohistochemistry and western-blot analyses to investigate protein expression. Two tuftelin mRNA transcripts and a single 64KDa protein were detected throughout embryonic development. Tuftelin was detected in tissues which develop from different embryonic origins; ectoderm, ectomesenchyme, and mesoderm. Tuftelin mRNA and protein were expressed already at E10.5, before the initiation of tooth formation and earlier than previously described. The expression pattern of tuftelin mRNA and protein exhibits dynamic spatio-temporal changes in various tissues. Tuftelin is expressed in neuronal tissues, thus fitting with its described correlation to nerve growth factor. A shift between cytoplasmatic and perinuclear/nuclear expression implies a possible role in regulation of transcription. Recent studies showed tuftelin is induced under hypoxic conditions in-vitro and in-vivo, through the hypoxia-inducible factor 1-α pathway. These results led to the hypothesis that tuftelin is involved in adaptation to hypoxic conditions. The fact that much of mammalian embryogenesis occurs at O ₂ concentrations of 1-5%, raises the possibility that tuftelin expression throughout development is due to its role in the adaptive mechanisms in response to hypoxia.

Tuftelin Is Required for NGF-Induced Differentiation of PC12 Cells

Nerve growth factor (NGF) promotes pleiotropic gene transcription-dependent biological effects, in neuronal and non-neuronal cells, including survival, proliferation, differentiation, neuroprotection, pain, and angiogenesis. It is hypothesized that during odontogenesis, NGF may be implicated in morphogenetic and mineralization events by affecting proliferation and/or differentiation of dental cells. Tuftelin belongs to the enamel associated teeth proteins and is thought to play a role in enamel mineralization. We previously reported that tuftelin transcript and protein, which are ubiquitously expressed in various tissues of embryos, adults, and tumors, were significantly upregulated during NGF-induced PC12 differentiation. To further confirm the involvement of tuftelin in the differentiation process, we established a tuftelin-knockdown neuronal PC12 cell model, using a non-cytotoxic siRNA directed towards sequences at the 3' UTR of the tuftelin gene. Using real-time PCR, we quantified tuftelin mRNA expression and found that tuftelin siRNA, but not scrambled siRNA or transfection reagents, efficiently depleted about 60% of NGF-induced tuftelin mRNA transcripts. The effect of tuftelin siRNA was quantified up to 6 days of NGF-induced differentiation. Using immunofluorescence and western blot analyses, we also found a direct correlation between reduction of 60-80% in tuftelin protein expression and inhibition of about 50-70% in NGF-induced differentiation of the cells, as was detected after 3-6 days of treatment. These results demonstrate an important role for tuftelin in NGF-induced differentiation of PC12 cells. Tuftelin could be a useful target for drug development in disease where neurotrophin therapy is required.

Evolutionary Analysis of the Mammalian Tuftelin Sequence Reveals Features of Functional Importance

Tuftelin (TUFT1) is an acidic, phosphorylated glycoprotein, initially discovered in developing enamel matrix. TUFT1 is expressed in many mineralized and non-mineralized tissues. We performed an evolutionary analysis of 82 mammalian TUFT1 sequences to identify residues and motifs that were conserved during 220 million years (Ma) of evolution. We showed that 168 residues (out of the 390 residues composing the human TUFT1 sequence) are under purifying selection. Our analyses identified several, new, putatively functional domains and confirmed previously described functional domains, such as the TIP39 interaction domain, which correlates with nuclear localization of the TUFT1 protein, that was demonstrated in several tissues. We also identified several sites under positive selection, which could indicate evolutionary changes possibly related to the functional diversification of TUFT1 during evolution in some lineages. We discovered that TUFT1 and MYZAP (myocardial zonula adherens protein) share a common ancestor that was duplicated circa 500 million years ago. Taken together, these findings expand our knowledge of TUFT1 evolution and provide new information that will be useful for further investigation of TUFT1 functions.

Expression of Clonorchis sinensis GIIIsPLA2 protein in baculovirus-infected insect cells and its overexpression facilitating epithelial-mesenchymal transition in Huh7 cells via AKT pathway

Although prior studies confirmed that group III secretory phospholipase A₂ of Clonorchis sinensis (CsGIIIsPLA₂) had stimulating effect on liver fibrosis by binding to LX-2 cells, large-scale expression of recombinant protein and its function in the progression of hepatoma are worth exploring. Because of high productivity and low lipopolysaccharides (LPS) in the Sf9-baculovirus expression system, we firstly used this system to express the coding region of CsGIIIsPLA₂. The molecular weight of recombinant CsGIIIsPLA₂ protein was about 34 kDa. Further investigation showed that most of the recombinant protein presented intracellular expression in Sf9 insect cell nucleus and could be detected only into cell debris, which made the protein purification and further functional study difficult. Therefore, to study the role of CsGIIIsPLA₂ in hepatocellular carcinoma (HCC) progression, CsGIIIsPLA₂ overexpression Huh7 cell model was applied. Cell proliferation, migration, and the expression level of epithelial-mesenchymal transition (EMT)-related molecules (E-cadherin, N-cadherin, α-catenin, Vimentin, p300, Snail, and Slug) along with possible mechanism were measured. The results indicated that CsGIIIsPLA₂ overexpression not only inhibited cell proliferation and promoted migration and EMT but also enhanced the phosphorylation of AKT in HCC cells. In conclusion, this study supported that CsGIIIsPLA₂ overexpression suppressed cell proliferation and induced EMT through the AKT pathway.

Expression of Functional Recombinant Human Tissue Transglutaminase (TG2) Using the Bac-to-Bac Baculovirus Expression System

PURPOSE

Tissue transglutaminase (TG2) is a unique multifunctional enzyme. The enzyme possesses enzymatic activities such as transamidation/crosslinking and non-enzymatic functions such as cell migration and signal transduction. TG2 has been shown to be involved in molecular mechanisms of cancers and several neurodegenerative diseases such as Alzheimer's disease. The present study aimed at cloning and expression of full length human TG2 in Bac-to-Bac baculovirus expression system and evaluation of its activity.

METHODS

pFastBac HTA donor vector containing coding sequence of human TG2 was constructed. The construct was transformed to DH10Bac for generating recombinant bacmid. The verified bacmid was transfected to insect cell line (Sf9). Expression of recombinant TG2 was examined by RT-PCR, SDS-PAGE and western blot analysis. Functional analysis was evaluated by fluorometric assay and gel electrophoresis.

RESULTS

Recombinant bacmid was verified by amplification of a band near to 4500 bp. Expression analysis showed that the enzyme was expressed as a protein with a molecular weight near 80 kDa. Western blot confirmed the presence of TG2 and the activity assays including flurometric assay indicated that the recombinant TG2 was functional. The electrophoresis assay conformed that the expressed TG2 was the indeed capable of crosslinking in the presence of physiological concentration calcium ions.

CONCLUSION

Human TG2 was expressed efficiently in the active biological form in the Bac-to-Bac baculovirus expression system. The expressed enzyme could be used for medical diagnostic, or studies which aim at finding novel inhibitors of the enzymes . To best of our knowledge, this is probably the first report of expression of full length human tissue transglutaminase (TG2) using the Bac-to-Bac expression system.

Expression of Functional Recombinant Human Tissue Transglutaminase (TG2) Using the Bac-to-Bac Baculovirus Expression System

PURPOSE

Tissue transglutaminase (TG2) is a unique multifunctional enzyme. The enzyme possesses enzymatic activities such as transamidation/crosslinking and non-enzymatic functions such as cell migration and signal transduction. TG2 has been shown to be involved in molecular mechanisms of cancers and several neurodegenerative diseases such as Alzheimer's disease. The present study aimed at cloning and expression of full length human TG2 in Bac-to-Bac baculovirus expression system and evaluation of its activity.

METHODS

pFastBac HTA donor vector containing coding sequence of human TG2 was constructed. The construct was transformed to DH10Bac for generating recombinant bacmid. The verified bacmid was transfected to insect cell line (Sf9). Expression of recombinant TG2 was examined by RT-PCR, SDS-PAGE and western blot analysis. Functional analysis was evaluated by fluorometric assay and gel electrophoresis.

RESULTS

Recombinant bacmid was verified by amplification of a band near to 4500 bp. Expression analysis showed that the enzyme was expressed as a protein with a molecular weight near 80 kDa. Western blot confirmed the presence of TG2 and the activity assays including flurometric assay indicated that the recombinant TG2 was functional. The electrophoresis assay conformed that the expressed TG2 was the indeed capable of crosslinking in the presence of physiological concentration calcium ions.

CONCLUSION

Human TG2 was expressed efficiently in the active biological form in the Bac-to-Bac baculovirus expression system. The expressed enzyme could be used for medical diagnostic, or studies which aim at finding novel inhibitors of the enzymes . To best of our knowledge, this is probably the first report of expression of full length human tissue transglutaminase (TG2) using the Bac-to-Bac expression system.

The C. elegans rab family: identification, classification and toolkit construction

Rab monomeric GTPases regulate specific aspects of vesicle transport in eukaryotes including coat recruitment, uncoating, fission, motility, target selection and fusion. Moreover, individual Rab proteins function at specific sites within the cell, for example the ER, golgi and early endosome. Importantly, the localization and function of individual Rab subfamily members are often conserved underscoring the significant contributions that model organisms such as Caenorhabditis elegans can make towards a better understanding of human disease caused by Rab and vesicle trafficking malfunction. With this in mind, a bioinformatics approach was first taken to identify and classify the complete C. elegans Rab family placing individual Rabs into specific subfamilies based on molecular phylogenetics. For genes that were difficult to classify by sequence similarity alone, we did a comparative analysis of intron position among specific subfamilies from yeast to humans. This two-pronged approach allowed the classification of 30 out of 31 C. elegans Rab proteins identified here including Rab31/Rab50, a likely member of the last eukaryotic common ancestor (LECA). Second, a molecular toolset was created to facilitate research on biological processes that involve Rab proteins. Specifically, we used Gateway-compatible C. elegans ORFeome clones as starting material to create 44 full-length, sequence-verified, dominant-negative (DN) and constitutive active (CA) rab open reading frames (ORFs). Development of this toolset provided independent research projects for students enrolled in a research-based molecular techniques course at California State University, East Bay (CSUEB).

The synthesis and characterization of cellular membrane affinity chromatography columns for the study of human multidrug resistant proteins MRP1, MRP2 and human breast cancer resistant protein BCRP using membranes obtained from Spodoptera frugiperda (Sf9) insect cells

CMAC (cellular membrane affinity chromatography columns) have been developed for the study of the human multidrug transporters MRP1, MRP2 and the breast cancer resistance protein (BCRP). The columns were constructed using the immobilized artificial membrane (IAM) stationary phase and cellular membrane fragments obtained from Spodoptera frugiperda (Sf9) cells that had been stably transfected with human Mrp1, Mrp2 or Bcrp cDNA, using a baculovirus expression system. The resulting CMAC(Sf9(MRP1)), CMAC(Sf9(MRP2)) and CMAC(Sf9(BCRP)) columns and a control column produced using membrane fragments from non-transfected Sf9 cells, CMAC(Sf9), were characterized using frontal affinity chromatography using [(3)H]-etoposide as the marker ligand and etoposide, benzbromarone and MK571 as the displacers on the CMAC(Sf9(MRP1)) column, etoposide and furosemide on the CMAC(Sf9(MRP2)) column and etoposide and fumitremorgin C on the CMAC(Sf9(BCPR)) column. The binding affinities (K(i) values) obtained from the chromatographic studies were consistent with the data obtained using non-chromatographic techniques and the results indicate that the immobilized MRP1, MRP2 and BCRP transporters retained their ability to selectively bind known ligands. (S)-verapamil displaced [(3)H]-etoposide on the CMAC(Sf9(MRP1)) column to a greater extent than (R)-verapamil and the relative IC(50) values of the enantiomers were calculated using the changes in the retention times of the marker. The observed enantioselectivity and calculated IC(50) values were consistent with previously reported data. The results indicated that the CMAC(Sf9(MRP1)), CMAC(Sf9(MRP2)) and CMAC(Sf9(BCRP)) columns can be used for the study of binding to the MRP1, MRP2 and BCRP transporters and that membranes from the Sf9 cell line can be used to prepare CMAC columns. This is the first example of the use of membranes from a non-mammalian cell line in an affinity chromatographic system.