Molecular cloning and characterization of a metal responsive Aedes aegypti intestinal mucin cDNA

Abstract

We have isolated a cDNA from Aedes aegypti that is transcribed in the larval midgut in response to metal exposure, and in the adult female midgut in response to iron or cadmium exposure, or a blood meal. The cDNA encodes a protein, designated Aedes aegypti intestinal mucin 1 (AEIMUC1), which has similarities with invertebrate intestinal mucins and peritrophins, and vertebrate mucins. Proline, serine and threonine comprise 30% of the amino acid composition of AEIMUC1, a characteristic of mucins. AEIMUC1 contains three cysteine-rich domains, two of which flank a proline/serine/threonine-rich domain, a feature shared by many mucin genes. This is the first report on the isolation of a metal-responsive gene from an aquatic insect.

The midgut epithelium of aquatic arthropods: a critical target organ in environmental toxicology.

“…AEIMUC1 exhibits similarity to these and other insect midgut proteins (10). The overall organization of the CRDs and the PTSB of our AEIMUC1 most closely resembles that of the moth larval intestinal mucin.…”

“…The fact that AEIMUC1 is induced by virus infection tends to support this hypothesis. Mucins are well known for their ability to bind pathogens such as viruses and bacteria, thereby inhibiting infection (10,21,(27)(28)(29)(30)(31). To overcome the mucin blockade, numerous pathogens have developed specific mucin-degrading enzymes (29,(34)(35)(36).…”

“…In Colorado it is estimated that heavy metals from over 5,000 abandoned waste dumps or tailing pipes impact over 2,600 km of streams (1). These hazardous waste sites expose aquatic organisms and other wildlife to multiple heavy metals as well as to other pollutants, which can exert impacts on aquatic ecosystems at different levels of organization (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Theoretically, organisms such as aquatic arthropods that experience long-term exposure to the mixtures would be most impacted by such heavy-metal pollution.…”

“…Concentrations and toxic effects of metals depend on the bioavailability of the metal and the size, age, sex, and developmental stage of the arthropod (2,6,8,10,11,18). Resistance to heavy metals varies with different genotypes and strains within a species (2,5-7).…”

Molecular cloning and expression of icarapin, a novel IgE‐binding bee venom protein

“…It was remarkable to find homology with a set of mostly unknown insect proteins, all sharing the same consensus sequence of 37-41 residues. One of these homologues is a putative salivary secreted mucin 3 from Aedes aegypti, but as icarapin has no regions rich in proline, threonine and serine residues occurring in clusters (in spite of its high Pro, Thr, Ser content of 21%) and cysteine residues are absent, it lacks some common features of mucins or mucin-like proteins [12].…”