Structural and functional analysis ofp27, a cuticular protein of Dirofilaria immitis that bears carboxy-terminal sequence homology with small heat shock proteins
Description
This project's strategic goal was to investigate the structure and function of p27, an antigenic protein of the filarial parasite Dirofilaria immitis. The notion that p27 could be functionally important was based on the following preliminary evidence: (1) it is homologous to small heat shock proteins; (2) it is abundantly transcribed; (3) it is present in the nematode cuticle; (4) it is antigenic in infected hosts; and (5) it is conserved among nematodes. The nematode cuticle is an extracellular matrix which forms a critical barrier between the parasite and host/vector defenses. We were interested in correlating the expression of p27 genes with the synthesis and elaboration of the cuticle during the infective larval stage molting process. To achieve this goal we established the following objectives: (1) isolate and characterize the structure of the p27 gene of D. immitis; (2) study the genomic organization of the p27 gene; (3) isolate the homologous p27 gene of Brugia malayi and compare the structure of both genes to the extensive data available on small heat shock genes from other organisms; and (4) to study the expression patterns of p27 in response to heat shock conditions and as a function of the L3-L4 molting process. Our findings indicate that p27 of D. immitis and B. malayi are members of the highly conserved small heat shock/$\alpha$-crystallin family of proteins. At least two unique genes have been identified in the D. immitis genome which may encode variant p27 isoforms, differing by perhaps the presence of a signal peptide. L3-L4 p27 gene products are expressed constitutively, and are not induced by heat shock conditions at 43$\sp\circ$C. The solubility characteristics of p27 are consistent with earlier findings that indicate it is a major component of the cuticle and is also found in the cytoplasm