Syntaxin 1 is expressed in the trout saccular hair cells: RT-PCR and immunocytochemical observations

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Abstract

Syntaxin is one of several proteins that may be involved in the docking of synaptic vesicles, synaptic vesicle recycling, and non-synaptic membrane trafficking. Presence of syntaxin has been reported in rat auditory and vestibular end organs. In the current study, we have examined the expression of message for syntaxin 1 in hair cells of the sacculus of the rainbow trout, Oncorhynchus mykiss, with RT-PCR using degenerate primers based on the sequence of zebrafish syntaxin. A PCR product of predicted size, 540 bp, yielded sequence with 94% amino acid identity to mouse, rat and human syntaxin and 96% identity to zebrafish syntaxin. An anti-syntaxin 1 primary antibody (S1172 Sigma) recognized a protein of 37 kDa, from the trout brain extract and the saccular hair cell homogenate in western blots. At the light microscopic level, immunoreactivity for anti-syntaxin 1 was observed within the sensory epithelium, in efferent fibers below the hair cells running parallel to the longitudinal axis of the saccule. In addition, sub- and supranuclear immunostaining was observed within select hair cells and immunoreactivity was concentrated at the base of stereocilliary arrays throughout. Immunogold electron microscopy further revealed that immunoreactivity was associated with the synaptic bodies and the basolateral and supranuclear regions of hair cells along with that present in the cuticular plate/stereocilliary regions of hair cells and efferent endings. These results suggest that syntaxin 1, expressed in the trout saccule, is associated not only with the docking of synaptic vesicles, but may be involved in vesicle recycling and in recycling of membrane.