Heat shock and developmental expression of hsp83 in the filarial nematode Brugia pahangi

Abstract

hsp83 was cloned from the filarial nematode Brugia pahangi. The mRNA was constitutively expressed at 37°C in life cycle stages that live in the mammalian host (microfilariae and adult worms). Heat shock resulted in only a minimal increase in levels of transcription. A genomic copy of hsp83 was isolated and was shown to contain 11 introns while sequencing of the 5′ upstream region revealed several heat shock elements. Using a chloramphenicol acetyltransferase (CAT) reporter gene construct the expression of hsp83 from B. pahangi (Bp-hsp83) was studied by transfection of COS-7 cells. Similar to the expression pattern in the parasite, CAT activity was detected at 37°C and was not influenced by heat shock. When the free-living nematode Caenorhabditis elegans was transfected with the same construct, CAT activity was not observed at normal growth temperatures (21°C) or under moderate heat shock conditions (28°C). However exposure to more severe heat shock (35°C) resulted in an increase in CAT activity. These results suggest that Bp-hsp83 has a temperature threshold ≥ 35°C for expression.