Characterization of the C. elegans erlin homologue

We first show that the C. elegans erlin homologue, ERL-1, is highly similar to mammalian erlins with respect to amino acid sequence, domain structure, biochemical properties and subcellular location. ERL-1 is present throughout the C. elegans embryo; in adult worms, ERL-1 appears restricted to the germline. The expression pattern of ERL-1 thus only partially overlaps with that of ITR-1, eliminating the possibility of ERL-1 being a ubiquitous and necessary regulator of ITR-1. We show that loss of ERL-1 does not affect overall phenotype, or alter brood size, embryonic development or defecation cycle length in either wild type or sensitized itr-1 mutant animals. Moreover we show that ERL-1 deficient worms respond normally to ER stress conditions, suggesting that ERL-1 is not an essential component of the general ERAD pathway.Although loss of erlin function apparently causes a strong phenotype in humans, no such effect is seen in C. elegans. C. elegans erlin does not appear to be a ubiquitous major modulator of IP3 receptor activity nor does erlin appear to play a major role in ERAD.Endoplasmic reticulum (ER) lipid raft associated proteins (erlins) were originally discovered by screening with antibodies prepared against isolated lipid raft proteins from human myelomonocytic cells [1]. Erlins associate with detergent resistant membranes but are located in the ER membrane, suggesting they are components of lipid raft-like domains in the ER membrane, not the plasma membrane. Erlins belong to the group of stomatin/prohibitin/flotillin/HflK/C (SPFH) domain containing proteins [1]. Members of this protein group differ in subcellular location and function, but share certain biochemical properties such as detergent resistant membrane association and the propensity to form oligomers [2].Erlins are conserved in both plants and animals [3] but so far erlin proteins have only been studied experimentally in mammalian cell lines [1,3-5]. Interestingly, no erlin homologues are found i