An RGDS peptide‐binding receptor, FR‐1R, localizes to the basal side of the ectoderm and to primary mesenchyme cells in sand dollar embryos

Abstract

Immunoblotting using polyclonal antibodies (pAb) raised against an FR-1 receptor (FR-1R), a 57 kDa Arg-Gly-Asp-Ser (RGDS)-binding protein, of the sand dollar Clypeaster japonicus showed that the pAb monospecifically bound to the protein. FR-1R was present in purified plasma membrane, suggesting that the protein is a membrane-bound protein. The molecular structure of FR-1R did not change throughout the early embryogenesis, whereas its expression changed significantly during this period. FR-1R was present in the cortex of unfertilized eggs and was then transferred to the hyaline layer soon after the fertilization. The hyaline layer retained FR-1R immunoreactivity during early embryogenesis. FR-1R appeared on the basal side of the ectoderm at the morula stage and was retained basolaterally, at least, to the early gastrula stage. In mesenchyme blastulae, FR-1R was also present on the surface of primary mesenchyme cells (PMC). FR-1R was localized on the basal side of the ectoderm in early gastrulae, exclusively at the place where PMC formed ventrolateral aggregates, and at the apical tuft ectoderm. In vitro, PMC bound to FR-1R and its binding was inhibited in the presence of a synthetic RGDS peptide or the pAb. The pAb introduced into the blastocoele perturbed PMC migration and gastrulation. FR-1R was weakly recognized by antihuman integrin beta5 subunit pAb.

Essential role of growth factor receptor‐mediated signal transduction through the mitogen‐activated protein kinase pathway in early embryogenesis of the echinoderm

“…1997; Yamasu et al . 2000; Katow & Sofuku 2001), the present severe inhibition of gastrulation by genistein occurred without visible perturbation of basal lamina formation, such as pamlin distribution. The presence of ECM suggests that exocytosis of ECM components was not affected by receptor‐type PTK.…”

“…1997), and has been localized on PMC and the basal surface of ectoderm (Katow et al . 1997; Katow & Sofuku 2001). This observation indicates the presence of an integrin‐like protein.…”

Mechanisms of the epithelial-to-mesenchymal transition in sea urchin embryos

“…The M r of the FR-1-binding protein (FR-1R) was 240 kDa; it contained 57 kDa subunits, and the epitope is recognized by an anti-human integrin b5 subunit antibody and an anti-sea urchin S. purpuratus integrin bL subunit antibody, but the bG subunit is not recognized. 97 However, the M r of FR-1R is distinctive from those of integrins; it is 120 kDa in S. purpuratus 84 and 140 kDa in aSU2 in L. variegatus, suggesting that integrins are not a sole group of fibronectin receptors. The fibronectin that is synthesized in PMCs is secreted into the blastocoel and binds to the surface of PMCs and the basal surface of the ectoderm through integrin and FR-1R, which is also expressed on the basal surface of the ectoderm.…”

Hyalin is a cell adhesion molecule involved in mediating archenteron–blastocoel roof attachment

“…These antisera are not available commercially and no other laboratory has prepared antisera against individually purified hyalin proteins. In addition, polyclonal antibodies have been reagents of choice in many studies using echinoderms (e.g., Hertzler and McClay, 1999;Wessel et al, 2000;Hoodbhoy et al, 2001;Katow and Sofuku, 2001). If monoclonal antibodies were used in the present study, many components of the large hyalin molecules would not have been recognized.…”