HSP43, a small heat-shock protein localized to specific cells of the vulva and spermatheca in the nematode Caenorhabditis elegans

A Differentiation Transcription Factor Establishes Muscle-Specific Proteostasis in Caenorhabditis elegans

Safeguarding the proteome is central to the health of the cell. In multi-cellular organisms, the composition of the proteome, and by extension, protein-folding requirements, varies between cells. In agreement, chaperone network composition differs between tissues. Here, we ask how chaperone expression is regulated in a cell type-specific manner and whether cellular differentiation affects chaperone expression. Our bioinformatics analyses show that the myogenic transcription factor HLH-1 (MyoD) can bind to the promoters of chaperone genes expressed or required for the folding of muscle proteins. To test this experimentally, we employed HLH-1 myogenic potential to genetically modulate cellular differentiation of Caenorhabditis elegans embryonic cells by ectopically expressing HLH-1 in all cells of the embryo and monitoring chaperone expression. We found that HLH-1-dependent myogenic conversion specifically induced the expression of putative HLH-1-regulated chaperones in differentiating muscle cells. Moreover, disrupting the putative HLH-1-binding sites on ubiquitously expressed daf-21(Hsp90) and muscle-enriched hsp-12.2(sHsp) promoters abolished their myogenic-dependent expression. Disrupting HLH-1 function in muscle cells reduced the expression of putative HLH-1-regulated chaperones and compromised muscle proteostasis during and after embryogenesis. In turn, we found that modulating the expression of muscle chaperones disrupted the folding and assembly of muscle proteins and thus, myogenesis. Moreover, muscle-specific over-expression of the DNAJB6 homolog DNJ-24, a limb-girdle muscular dystrophy-associated chaperone, disrupted the muscle chaperone network and exposed synthetic motility defects. We propose that cellular differentiation could establish a proteostasis network dedicated to the folding and maintenance of the muscle proteome. Such cell-specific proteostasis networks can explain the selective vulnerability that many diseases of protein misfolding exhibit even when the misfolded protein is ubiquitously expressed.

Molecular chaperones protect proteins from misfolding and aggregation. In multi-cellular organisms, the composition and expression levels of chaperones vary between tissues. However, little is known of how such differential expression is regulated. We hypothesized that the cellular differentiation that regulates the cell-type specific expression program may be involved in establishing a cell-type specific chaperone network. To test this possibility, we addressed the myogenic commitment transcription factor HLH-1 (CeMyoD) that converts embryonic cells to muscle cells in Caenorhabditis elegans. We demonstrated that HLH-1 regulates the expression of muscle chaperones during muscle differentiation. Moreover, we showed that HLH-1-dependent expression of chaperones is required for embryonic development and muscle function. We propose that cellular differentiation results in cell-specific differences in the chaperone network that may be detrimental in terms of the susceptibility of neurons and muscle cells to protein misfolding diseases.

A cell line derived from the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae)

The red flour beetle, Tribolium castaneum, is a model organism for agricultural and medical research and its complete genome is sequenced. We established a continuously replicating T. castaneum cell line to complement existing physiological, genetic, and genomic research tools. We set up trial cell cultures from egg, pupa, and adult stages as tissue sources and incubated them in six separate cell culture media to determine the optimal combination of tissue source and medium for cell replication. Our most promising culture was generated by co-culturing adult (∼75 %) and pupal tissues in EX-CELL 420 medium containing 9 % FBS. Our new cell culture is designated BCIRL-TcA-CLG1 (TcA) and it has been subcultured more than 90 times. Amplification of genomic DNA with species-specific primers yielded DNA fragments of the expected sizes and with sequences identical to those from the published Tribolium genome. Additionally, we characterized this line using DNA fingerprinting (DAF-PCR) and compared it with three other coleopteran cell lines and its conspecific pupae to confirm identity. Its doubling time is 155.2 hr. Early passages consisted of attached cells and vesicles in suspension, whereas later passages consisted primarily of attached, spherical cells. Similar to other established cell lines, the ploidy of TcA cells was variable, ranging from 20 chromosomes/cell (diploid) to above 30 chromosomes/cell. TcA cells withstood incubation at 40°C for 1 h with no decrease in viability. We recorded increased levels of one heat shock protein (43 kDa) and of the hsp68a transcript following exposure to 40°C. Taken together, this represents the first report of a continuously replicating T. castaneum cell line. We expect the BCIRL-TcA-CLG1 line will become a useful tool in Tribolium research.

Molecular cloning and characterization of a C-type lectin from Ancylostoma ceylanicum: evidence for a role in hookworm reproductive physiology

Lectins comprise a family of related proteins that mediate essential cell functions through binding to carbohydrates. Within this protein family, C-type lectins are defined by the requirement of calcium for optimal biologic activity. Using reverse transcription PCR, a cDNA corresponding to a putative C-type lectin has been amplified from the hookworm parasite Ancylostoma ceylanicum. The 550 nucleotide open reading frame of the A. ceylanicum C-type Lectin-1 (AceCTL-1) cDNA corresponds to a 167 amino acid mature protein (18,706 Da) preceded by a 17 amino acid secretory signal sequence. The recombinant protein (rAceCTL-1) was expressed in Drosophila S2 cells and purified using a combination of affinity chromatography and reverse phase HPLC. Using in vitro carbohydrate binding studies, it was determined that rAceCTL-1 binds N-acetyl-d-glucosamine, a common component of eukaryotic egg cell membranes. Using a polyclonal IgG raised against the recombinant protein, the native AceCTL-1 was identified in sperm and soluble protein extracts of adult male A. ceylanicum by immunoblot. Probing of adult hookworm sections with the polyclonal IgG demonstrated localization to the testes in males, as well as the spermatheca and developing embryos in females, consistent with its role as a sperm protein. Together, these data strongly suggest that AceCTL-1 is a male gender-specific C-type lectin with a function in hookworm reproductive physiology.

Construction of gender-enriched cDNA archives for adult Oesophagostomum dentatum by suppressive-subtractive hybridization and a microarray analysis of expressed sequence tags

In the present study, we constructed gender-enriched cDNA libraries for the adult stage of the parasitic nematode Oesophagostomum dentatum (order Strongylida) using suppressive-subtractive hybridization (SSH), sequenced clones from the female-library and male-library (480 from each) and conducted bioinformatic and microarray analyses of the expressed sequence tags (ESTs). In total, 873 ESTs (440 male and 433 female) were obtained, achieving a sequencing success of 91%The nucleotide sequences reported in this article (Tables 1-5) have been deposited in the EMBL, GenBank and DDJB databases under the Accession nos. AM157797-AM158083. Microarray analyses of 516 unique ESTs representing both gender-enriched libraries revealed differential hybridization for 391 of them (75.8%). Of these, 220 (56.3%) had significantly greater signal intensities in the female than in the male, and 154 (70%) of these were predicted to have homologues in C. elegans. These homologues were predicted to be involved in key biological processes, including embryonic nutrition, gametogenesis, molecular binding/transport or metabolism, nucleic acid synthesis and function, and signal transduction. Of the 171 ESTs with statistically higher signal intensities in male O. dentatum, 43.8% had homologues in C. elegans. These homologues included major sperm proteins (MSPs) or MSP-like molecules, keratin-like molecules, molecules involved in metabolism, PDZ domain-containing proteins, sugar binding proteins, protein kinases, serine proteases or protease inhibitors, molecules involved in proteolysis and other proteins, such as enzymes and various putative proteins. Of the 287 ESTs (from both gender-enriched cDNA libraries) with no known homologues in C. elegans, 50 (17.4%) had homologues in other nematodes, 8 had homologues in various other organisms and 104 (36.2%) had no homology to any sequence in current gene databases. The present study lays a foundation for the isolation and molecular, biochemical and functional characterization of selected genes from the gender-enriched cDNA archives established for O. dentatum.

Association of several small heat-shock proteins with reproductive tissues in the nematode Caenorhabditis elegans

Immunohistochemical data on 10 of the 14 small heat-shock (smHSPs) proteins in fourth larval stage and adult Caenorhabditis elegans show that the tissues expressing the greatest number of smHSPs are vulva (HSP12s, HSP43 and, under stress, HSP16s) and spermatheca (HSP12s, HSP25, HSP43 and, under stress, HSP16s). HSP43 is also expressed in male tail structures, and following heat-shock HSP16s are expressed in spermatids and spermatozoa.