An 11-ketotestosterone induced kidney-secreted protein: the nest building glue from male three-spined stickleback, Gasterosteus aculeatus

In male three-spined sticklebacks, Gasterosteus aculeatus, the kidney hyper trophies during the breeding season and produces a glue which is used in ne st-building. This hypertrophy is androgen dependent with 11-ketotestosteron e (II KT) being most effective. The aim of the present study was to charact erize the protein composition of this glue. Threads of glue were collected from stickleback nests and glue material was sampled from the content of ur inary bladders of male sticklebacks in breeding condition. The samples were investigated using sodium dodecyl sulphate-polyacrylamide gel electrophore sis (SDS-PAGE). One major glycoprotein dominated in both the nest-threads a nd urinary bladder samples. The identified glycoprotein had a molecular mas s of approximately 203 kDa. After deglycosylation the molecular mass was ap proximately 200 IrDa. The amino acid composition of the protein from urinar y bladder content was almost identical to the amino acid composition of the protein from the nest-threads. The protein had a relatively high content o f cysteine (7.6-8.0%). The glycoprotein was named spiggin. Spiggin was abse nt in the urinary bladder of untreated castrated fish, but spiggin was pres ent in sham-operated fish and in castrated fish treated with 11 KT. These r esults demonstrate that spiggin is induced by II KT. Spiggin is so far the only protein known to be induced by 11KT and based on the present findings we suggest that spiggin represents a novel structural protein.