Abstract
Store-operated Ca(2+) influx has recently been shown to require the activation of two proteins, stromal interaction molecule 1 (STIM1) and Orai1. In mammals the putative channel ion selectivity filter is thought to comprise conserved charged residues in the first and third transmembrane domains of Orai1 in addition to three residues in the first extracellular loop. The latter residues, however, are not conserved in either of the Bombyx mori Orai1 variants or in most insects, suggesting that selectivity is a relatively recent evolutionary event. In B. mori, thapsigargin-mediated STIM1 redistribution is dependent on a cluster of highly conserved basic residues (amino acids 380-385) in the C terminus that likely interact with acidic residues in the Orai1 C terminus. BmSTIM1 redistribution in vitro also occurs downstream of pheromone biosynthesis activating neuropeptide receptor activation. Activation of in vivo RNA interference mechanisms confirmed the physiological role of BmSTIM1 and Orai1 in sex pheromone production.