Abstract
BackgroundThe founding member of the EMAP-like protein family is the Echinoderm Microtubule-Associated Protein (EMAP), so-named for its abundance in sea urchin, starfish, and sand dollar eggs. The EMAP-like protein family has five members in mammals (EML1 through EML5) and only one in both Drosophila (ELP-1) and C. elegans (ELP-1). Biochemical studies of sea urchin EMAP and vertebrate EMLs implicate these proteins in the regulation of microtubule stability. So far, however, the physiological function of this protein family remains unknown.ResultsWe examined the expression pattern of C. elegans ELP-1 by means of transgenic gene expression in living embryos and adults, and by immunolocalization with an ELP-1-specific antibody in fixed tissues. In embryos, ELP-1 is expressed in the hypodermis. In larvae and adults, ELP-1 is expressed in the body wall, spermatheca and vulval muscles, intestine, and hypodermal seam cells. In muscle, ELP-1 is associated with adhesion complexes near the cell surface and is bound to a criss-crossing network of microtubules in the cytoplasm. ELP-1 is also expressed in a subset of mechanoreceptor neurons, including the ray neurons in the male tail, microtubule-rich touch receptor neurons, and the six ciliated IL1 neurons. This restricted localization in the nervous system implies that ELP-1 plays a role in mechanotransmission. Consistent with this idea, decreasing ELP-1 expression decreases sensitivity to gentle touch applied to the body wall.ConclusionThese data imply that ELP-1 may play an important role during the transmission of forces and signals between the body surface and both muscle cells and touch receptor neurons.
Highlights
The founding member of the EMAP-like protein family is the Echinoderm Microtubule-Associated Protein (EMAP), so-named for its abundance in sea urchin, starfish, and sand dollar eggs
Our results indicate that ELP-1 is expressed in cells that make productive interactions with the extracellular matrix, including but not limited to the hypodermis, body wall muscles, male-specific sex muscles, and the microtubulerich touch receptor neurons
Results elp-1 encodes the sole C. elegans member of the EMAPlike protein family All of the EMAP-like proteins identified to date, including vertebrate EMLs and invertebrate ELPs, share a common domain organization with a short, 60–70 amino acid, hydrophobic EMAP-like protein (HELP) motif preceded by a series of WD repeat domains (Figure 1)
Summary
The founding member of the EMAP-like protein family is the Echinoderm Microtubule-Associated Protein (EMAP), so-named for its abundance in sea urchin, starfish, and sand dollar eggs. The EMAP-like protein family has five members in mammals (EML1 through EML5) and only one in both Drosophila (ELP-1) and C. elegans (ELP-1). The founding member of the EMAP-like protein family is the 75 kDa Echinoderm Microtubule-Associated Protein (EMAP), so-named for its abundance in sea urchin, starfish, and sand dollar eggs [7]. In certain patients with T-cell acute lymphoblastic leukemia (TALL), the gene encoding the nonreceptor protein kinase (c-ABL1) is fused to the EML1 gene on chromosome 14, which causes expression of an EML1-ABL1 fusion protein, that functions as a dysregulated tyrosine kinase [14]. The N-terminal coiled-coil domain of EML1 is required for kinase activation, which suggests that oligomerization of EML1 is required for the function of EML1-ABL1 fusion proteins
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