ROLES OF P24 PROTEINS IN GLYCOSYLATION AND EXTRACELLULAR SIGNALING PATHWAYS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Complex carbohydrates on cell surface and extracellular proteins play essential roles in molecular recognition events critical to cell growth and differentiation. In humans, the emerging congenital disorders of glycosylation (CDGs) include severe multisystemic syndromes linked to abnormal protein glycosylation; most of the identified CDGs reflect disruptions of glycan biosynthetic pathways. Recent studies have revealed that glycosylation abnormalities and CDG clinical presentations can also be caused by defects in intracellular protein trafficking. Genetically tractable simple organisms provide an opportunity to study the regulatory mechanisms of these conserved pathways. We have identified three genes in the nematode Caenorhabditis elegans which, when mutated, elicit binding of the lectin Wheat Germ Agglutinin on the cuticle surface, suggesting a role in the modulation of one or more glycosylation pathways. These mutations inactivate members of a conserved protein family (p24) implicated in cargo selectivity of endoplasmic reticulum to Golgi transport. Interestingly, these mutants exhibit specific neuronal abnormalities (our preliminary results), offering the opportunity to explore the role of p24 activity on the development of the nervous system. We use genetic and biochemical approaches in C. elegans to pursue the following aims: 1) examine the relationship between p24 activity and protein glycosylation status, by analysis of metabolically labeled glycoproteins from wild type and mutant embryonic cells and lectin purified fractions; 2) explore extracellular signaling pathways as downstream targets of p24 activity, using double mutant analysis; and 3) exploit abnormal lectin binding to the cuticle surface to identify additional genes involved in surface protein glycosylation and trafficking.