Hong L et al. (2001), MUP-4 is a novel transmembrane protein with fun...

ECB-ART-37874

J Cell Biol 2001 Jul 23;1542:403-14. doi: 10.1083/jcb.200007075.

Show Gene links Show Anatomy links

MUP-4 is a novel transmembrane protein with functions in epithelial cell adhesion in Caenorhabditis elegans.

Hong L , Elbl T , Ward J , Franzini-Armstrong C , Rybicka KK , Gatewood BK , Baillie DL , Bucher EA .

???displayArticle.abstract???
Tissue functions and mechanical coupling of cells must be integrated throughout development. A striking example of this coupling is the interactions of body wall muscle and hypodermal cells in Caenorhabditis elegans. These tissues are intimately associated in development and their interactions generate structures that provide a continuous mechanical link to transmit muscle forces across the hypodermis to the cuticle. Previously, we established that mup-4 is essential in embryonic epithelial (hypodermal) morphogenesis and maintenance of muscle position. Here, we report that mup-4 encodes a novel transmembrane protein that is required for attachments between the apical epithelial surface and the cuticular matrix. Its extracellular domain includes epidermal growth factor-like repeats, a von Willebrand factor A domain, and two sea urchin enterokinase modules. Its intracellular domain is homologous to filaggrin, an intermediate filament (IF)-associated protein that regulates IF compaction and that has not previously been reported as part of a junctional complex. MUP-4 colocalizes with epithelial hemidesmosomes overlying body wall muscles, beginning at the time of embryonic cuticle maturation, as well as with other sites of mechanical coupling. These findings support that MUP-4 is a junctional protein that functions in IF tethering, cell-matrix adherence, and mechanical coupling of tissues.

???displayArticle.pubmedLink??? 11470827
???displayArticle.pmcLink??? PMC2150763
???displayArticle.link??? J Cell Biol

Species referenced: Echinodermata
Genes referenced: LOC100887844 LOC100889782 LOC105441151 LOC115918117 LOC115919910 LOC115925415 LOC579769 LOC590297 span

???attribute.lit??? ???displayArticles.show???

	Figure 1. Disposition of muscle and hypodermal tissues in C. elegans . (A) Diagram of a cross-section of an adult worm illustrating the muscle–hypodermal-cuticular relationships, which are established by the end of embryogenesis (adapted from Costa et al., 1997). (B) Schematic diagram of the relationship of a body–wall muscle sarcomere and overlying hypodermis (adapted from Hresko et al., 1994). (C) EM of N2 worm illustrating the annuli ridges (arrow demarcates the furrows between the ridges) and the relationship of hypodermis and muscle (arrowhead).
	Figure 2. Body wall muscles in WT and mup-4 and mua-3 mutant worms. (A–F) Animals were fixed and stained with rhodamine-conjugated phalloidin to visualize filamentous actin and thus highlight the body wall muscles that span the length of the animal on both dorsal and ventral sides. Arrows indicate dorsal; arrowheads, ventral. (A) WT adult and L1 larva (). mup-4(ar60) (B) and mup-4(s2426) (C) threefold-arrested embryos. Note complete displacement of dorsal muscles to the ventral side and retraction of the ventral muscles from the anterior and posterior ends. The bright muscle remaining in the head is the pharyngeal muscle. (D) Larva soaked with mup-4 dsRNA becomes an adult with localized muscle displacement. F1 progeny of a soaked worm exhibiting the Mup phenotype. (E) mua-3(ar62) mutant larva with localized muscle displacement. (F) Larva soaked with mua-3 dsRNA shows localized muscle displacement as an adult. (G) GFP fluorescence of the mup-4::gfp transgene in a Mua F1 progeny resulting from injection of mua-3 dsRNA into strain EE86. Note that the hypodermal mup-4::gfp fluorescence appears primarily localized with the displaced muscle.
	Figure 3. (A) The localization and structure of the mup-4 locus relative to the physical map. The cosmids/fosmid as shown represent the actual clone boundaries. Sequences assigned to clone names in ACEDB do not reflect these boundaries. The deletion identified in the allele mup-4(s2426) deficiency is indicated. (B) Schematic representation of the protein structure of MUP-4 with domain key.
	Figure 4. Alignment of 28 cysteine-rich motifs in MUP-4. Dark highlights indicate identical amino acids, and light highlights indicate conservative changes. The EGF motif is comprised of a characteristic pattern of six cysteines and forms a globular domain stabilized by disulfide bridges (Davis, 1990). A consensus for the MUP-4 EGF-like repeats is shown (Herz et al., 1988). The consensus specific to the Ca2+-binding EGF subclass (EGF-CB) to which Mup-4 repeats 2, 3, 4, 7, 14, 15, 16, 18, 19, 20, 21, 25, 26, and 27 belong (according to Rees et al., 1988), and a consensus shared by the MUP-4 EGF-like repeats are also shown. The first 27 repeats appear as a hybrid of EGF-like classes, as defined by their spacing of six cysteines and conserved residues: before the fourth cysteine, the spacing is more like B.1, whereas after the fifth cysteine, it is more like B.2. In places where an intervening number of residues is less variant, the number most often found is listed. The position of each EGF-like motif in the amino acid sequence is shown in the last column. The juxtaposition of EGF-like domains is close, most being separated by only a few amino acids, with the exception of 67 amino acids between repeats 9 and 10. Other larger spacings reflect the interspersed vWFA and SEA domains (see Figs. 3 B and 5, A and B).
	Figure 5. Alignments of MUP-4 to the vWFA domain, SEA module, and filaggrin. For each amino acid sequence comparison, a consensus is shown as the last line. Similarities are highlighted as described in the legend to Fig 4. (A) Comparison of vWFAs of MUP-4, MUA-3 (Bercher et al., 2001), one repeat (VA) of chicken type XII collagen (Yamagata et al., 1991), and one repeat of human vWFA (Mancuso et al., 1989). MUP-4 is most similar to MUA-3 (81%) and type XII collagen (50%). (B) Comparison of the two SEA modules in MUP-4 and MUA-3 and from enterokinase (Matsushima et al., 1994). (C) MUP-4 intracellular domain: homology to human filaggrin (Gan et al., 1990) and 30 amino acids of MUA-3 (Bercher et al., 2001). The underlined portion highlights a repeated section from filaggrin. Putative phosphorylation sites are highlighted.
	Figure 6. MUP-4 expression in WT and mutant threefold embryos. Triple staining patterns of the 5-6.1.1 mAb to the muscle protein myosin heavy chain A (MHCA) (A, C, and E), the MH27 mAb to epithelial adherens junctions (A, C, and E), and the MUP-4 polyclonal antibody to the intracellular domain of MUP-4. (B, D, and F) Arrows highlight the same region of the embryo. (A and B) WT embryo in which MUP-4 can be seen in some regions as circumferential rings overlying the muscle. Pharyngeal staining of MH27 is visible in A (thick arrow), whereas strong pharyngeal staining of MUP-4 is not seen in B. A background of general hypodermal cell staining is also observed in this animal. (C–F) Lateral views of mup-4(ar60) and mup-4(mg36) mutant embryos, respectively, with the characteristic muscle displacement (C and E, arrowheads). Mutants do not show the annuli-like pattern (D and F).
	Figure 7. MUP-4 expression in larvae. (A) Lateral view of an N2 larva (L2) stained with a MUP-4 antibody. Arrows mark staining of MUP-4 in circumferential rings, arrowheads mark B cell perinuclear staining. (B) Lateral view of an L2 larvae MUP-4::GFP expression in an integrated mup- 4::gfp line (EE82). Arrows mark staining in circumferential rings, arrowheads mark B cell perinuclear staining. Small arrow marks diffuse hypodermal cell staining in hypodermal cells overlying muscle. (C) Head of an L1 larva showing MUP-4::GFP fluorescence (EE73; arrow). (D) Confocal overlay of immunolocalization of MUP-4 (red) and MH27 and MHCA (green). MH27 demarcates seam cell boundary (arrowhead). (E–G) Confocal analysis of an L3 larva stained with MUP-4 and MH4 showing localization to circumferential rings (arrows) and the touch neuron (arrowheads). The confocal overlay (G) shows partial colocalization.
	Figure 8. Transmission EM analysis of mup-4(ar60) (A and B) and the mup-2(e2346ts) control (C and D). Dorsal is up and ventral is down. In each panel, the white arrows highlight muscle. (A) Illustrates the characteristic appearance of a mup-4(ar60) mutant. On the dorsal side, the hypodermis is not attached to the dorsal cuticle (black arrow), and no muscle remains on the dorsal side. On the ventral bent surface, the cuticle is raised into large folds (arrowheads), whereas the hypodermis has a smooth outline without any obvious attachment to the folded cuticle that is normally observed (as in C and D). (B) Illustrates a typical high magnification view of the ventral surface with the arrowhead indicating the abnormal flat hypodermal surface (*) lacking attachment to the cuticle. (C) Illustrates the characteristic appearance of the dorsal surface of a mup-2(e2346ts)/TnT-1 mutant. Displaced muscle is seen (white arrowheads) traversing the larva. Notably, the apical hypodermal membrane above this displaced muscle is still attached normally to the cuticle and densities characteristics of junctional complexes are evident (black arrow). (D) Illustrates a ventral view of a bent mup-2 animal. In contrast to mup-4 mutants (A and B), the ventral hypodermal membrane is not smooth, but folds upward toward the cuticle ridges. Similar to the dorsal surface, the apical hypodermis shows densities representative of junctional complexes. WT controls (Fig. 1 C; data not shown) show hypodermal–cuticle relationships similar to mup-2 controls (Francis and Waterston, 1985, 1991).

References [+] :

Argos, Prediction of protein structure. 1986, Pubmed