Molecular Fingerprinting of Carbohydrate Structure Phenotypes of Three Porifera Proteoglycan-like Glyconectins

Abstract

Glyconectins (GNs) represent a new class of proteoglycan-like cell adhesion and recognition molecules found in several Porifera species. Physico-chemical properties of GN carbohydrate moieties, such as size, composition, and resistance to most glycosaminoglycan-degrading enzymes, distinguish them from any other type of known glycoproteins. The molecular mechanism of GN-mediated self/non-self discrimination function is based on highly species-specific and Ca 2؉ -dependent GN to GN associations that approach the selectivity of the evolutionarily advanced immunoglobulin superfamily. Carbohydrates of glyconectins 1, 2, and 3 are essential for species-specific auto-aggregation properties in three respective Porifera species. To obtain a structural insight into the molecular mechanisms, we performed carbohydrate structural analyses of glyconectins isolated from the three sponge model systems, Microciona prolifera (GN1), Halichondria panicea (GN2), and Cliona celata (GN3). The glycan content of all three GNs ranged between 40 and 60% of their total mass. Our approach using sequential and selective chemical degradation of GN glycans and subsequent mass spectrometric and NMR analyses revealed that each glyconectin presents novel and highly species-specific carbohydrate sequences. All three GNs include distinct acid-resistant and acid-labile carbohydrate domains, the latter composed of novel repetitive units. We have sequenced four short sulfated and one pyruvilated unit in GN1, eight larger and branched pyruvilated oligosaccharides in GN2, which represent a heterogeneous but related family of structures, and four sulfated units in GN3.Porifera glyconectins (GNs) 1 are emerging as a new class of proteoglycan-like cell adhesion and recognition molecules. In the preceding article (22) the molecular mechanism of GNmediated self/non-self discrimination was shown to be based on highly species-specific and Ca 2ϩ -dependent glyconectin to glyconectin associations operating via carbohydrates. The selectivity of these macromolecular interactions approached that of the immunoglobulin superfamily. Based on these findings xeno-selectivity of GN to GN recognition in Porifera, the closest existing relatives to the primordial multicellular organisms, was proposed to be a new self-assembly paradigm in the cellular adhesion and recognition pathway during the evolution of multicellular forms of life and the divergence of species.Early work on purified carbohydrates of Microciona prolifera glyconectin 1, published in 1987 and 1993 (1, 2) and followed by experiments on synthetic oligosaccharide epitopes in 2001 (3), showed that GN1 functions in cell aggregation via glycan to glycan interactions. Although the carbohydrates of GN2 and GN3, purified from Halichondria panicea and Cliona celata, respectively, are functional in cell adhesion and recognition, it remains to be demonstrated whether they operate as GN1 through glycan to glycan associations. An analogous molecular mechanism of carbohydrate-carbohydrate binding involvement in cell adhes...

Polissacarídeos da biodiversidade brasileira: uma oportunidade de transformar conhecimento em valor econômico

“…Vários grupos de pesquisa vêm se dedicando ao estudo de polissacarídeos extraídos de invertebrados marinhos, [137][138][139][140][141][142][143] 150 O Agaricus blazei, que é um cogumelo comestível -conhecido popularmente como cogumelo do sol, representa um caso emblemático. Ele é oriundo das regiões serranas do sul do estado de São Paulo.…”

Molecular Recognition between Glyconectins as an Adhesion Self-assembly Pathway to Multicellularity

“…The rest of the size-heterogeneous population of GN3 polysaccharides showing tailing from the 110 kDa glycan band on the gel is most likely either the result of degradation or the unfinished synthesis product of this major glycan species (see accompanying article (40)). We cannot completely exclude the possibility that this product is also mixed with some less abundant yet undefined polysaccharide species.…”

“…This will require a new methodology to take into account the spacing of glycan chains, their internal sequences and charge distribution, as well as the peptide sequences of the core protein (which greatly influence enzymatic and chemical cleavage). Our structural data of GN polysaccharides presented in the accompanying article (40) promote the development of sequencing techniques applicable to novel classes of glycans. Such potential methods, when used on the purified GN fragments close to the core protein together with cloning of the GN genes, will definitively confirm the exact nature of GN glycan core and linkage to protein.…”

“…In conclusion, NMR and enzymological data together with compositional and electrophoretic analyses specify that three GN carbohydrates have a novel type of species-specific and repetitive structure residing in the large acidic polysaccharides. More detailed chemical sequence analyses of GN glycans combined with NMR and mass spectrometry are described in the accompanying article (40).…”

“…5). These sequences were established by mass spectrometry analyses (reported in the article (40)). The large size and great complexity of the GN glycans do not allow identification of the complete arrangement of these sequences within the polymer.…”