Developmentally regulated expression of a unique small heat shock protein in Brugia malayi

A screen of an expression library from the fourth larval stage (L4) of the parasitic nematode Brugia malayi resulted in the identification of a 727 bp full-length cDNA with 29-40% identity to members of the small heat shock f amily of proteins (Bm-hsp-s1). The open reading frame encoded a protein of approximately 18 kDA (Bm-HSP-s1). An alignment of the Bm-HSP-s1 sequence wi th the sequences of small HSPs from vertebrate and invertebrate species dem onstrated that a majority of the identity was concentrated in the central a lpha-crystallin domain. Bm-HSP-s1 was constitutively produced by L4 and adu lt parasites and at low levels by third-stage larvae (L3), but not by first -stage larvae (microfilariae). In adult parasites, Bm-HSP-s1 was localized to the body wall muscle cells and to the cells of the hypodermis/lateral co rd. Bm-HSP-s1 production was induced in adult and L3 incubated at 42 degree s C and in L3s during the developmental transition from vector-stage to ver tebrate-stage parasites at 37 degrees C. Neither increased nor decreased te mperatures induced Bm-HSP-s1 production in microfilariae. Nitric oxide indu ced low-level, transient Bm-HSP-s1 synthesis in adults, but not in microfil ariae. Bm-HSP-sl did not function as a molecular chaperone to prevent heat- induced aggregation of a test substrate. The developmentally regulated expr ession and inducable nature of Bm-HSP-s1 suggests that it may have a stage- restricted role in maintaining parasite homeostasis. (C) 1999 Elsevier Scie nce B.V. All rights reserved.