Localization of prosaposin in rat cochlea

• Published in: Neuroscience research Vol. 57; no. 3; pp. 372 - 378
• Main Authors: Terashita, Takehiro, Saito, Shouichiro, Miyawaki, Kyojy, Hyodo, Masamitsu, Kobayashi, Naoto, Shimokawa, Tetsuya, Saito, Kyoko, Matsuda, Seiji, Gyo, Kiyofumi
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01-03-2007
• Subjects: Animals; Cathepsin D - metabolism; Cell Survival - physiology; Cochlea; Cochlea - metabolism; Cochlea - ultrastructure; Female; Hair Cells, Auditory - metabolism; Hair Cells, Auditory - ultrastructure; Homeostasis - physiology; Immunoreactivity; Lysosomes - metabolism; Lysosomes - ultrastructure; Male; Microscopy, Immunoelectron; Nerve Growth Factors - metabolism; Neurons, Afferent - metabolism; Neurons, Afferent - ultrastructure; Organ of Corti - metabolism; Organ of Corti - ultrastructure; Prosaposin; Rats; Rats, Wistar; RNA, Messenger - metabolism; Saposins - biosynthesis; Saposins - genetics; Spiral Ganglion - metabolism; Spiral Ganglion - ultrastructure; Stria Vascularis - metabolism; Stria Vascularis - ultrastructure; Cochlea; Prosaposin; Immunoreactivity
• ISSN: 0168-0102; 1872-8111
• DOI: 10.1016/j.neures.2006.11.006

Prosaposin, the precursor of the sphingolipid hydrolase activator proteins called saposins A, B, C, and D, is abundant in the nervous system and muscles. Besides its role as the precursor of saposins, prosaposin is reported to function as a neurotrophic factor, initiating neural differentiation and preventing neuronal cell death
in vivo and
in vitro. In this study, we examined the localization and synthesis of prosaposin in the rat cochlea. Intense prosaposin immunoreactivity was observed in the organ of Corti, stria vascularis, and spiral ganglion. In an immuno-electron microscopic study, prosaposin immunoreactivity was found mainly in lysosomal granules of the cells in these regions. In the lysosome, prosaposin does not always colocalize with cathepsin D, but was localized mainly in the dark area of the lysosome. Prosaposin mRNA was observed in these same regions. Our results suggest that prosaposin plays a role in homeostasis in the peripheral auditory system.