Recognition of Phosphatidylserine on the Surface of Apoptotic Spermatogenic Cells and Subsequent Phagocytosis by Sertoli Cells of the Rat

doi:10.1074/jbc.272.4.2354

Recognition of Phosphatidylserine on the Surface of Apoptotic Spermatogenic Cells and Subsequent Phagocytosis by Sertoli Cells of the Rat*

From the ^‡ Graduate School of Natural Science and Technology and the
^¶ Faculty of Pharmaceutical Sciences, Kanazawa University, Takara-machi, Kanazawa, Ishikawa 920, Japan and the
^§ Department of Inflammation Research, Tokyo Metropolitan Institute of Medical Science, Honkomagome, Bunkyo-ku, Tokyo 113, Japan

Abstract

In a primary co-culture of spermatogenic and Sertoli cells of the rat, many spermatogenic cells die by apoptosis and are subsequently engulfed by Sertoli cells. We investigated the mechanism of this phagocytosis reaction. Testicular cells from 20-day-old rats were cultured, and spermatogenic cells and Sertoli cells were separated. When the recovered spermatogenic cells were maintained without Sertoli cells, the viability of the cells decreased and they became more susceptible to phagocytosis by Sertoli cells. Phagocytosis was severely impaired when liposomes containing acidic phospholipids, such as phosphatidylserine, phosphatidylinositol, and cardiolipin, were included in the reaction, whereas those consisting of neutral phospholipids showed little effect. Such anionic liposomes were more efficiently engulfed by Sertoli cells than were the other neutral liposomes. Also, the number of spermatogenic cells that exposed phosphatidylserine to the surface increased when cells were maintained in single culture. The results indicate that upon induction of spermatogenic cell apoptosis, phosphatidylserine and probably other acidic phospholipids, which are normally localized in the inner leaflet of the plasma membrane, translocate to the outer leaflet and serve as a signal for phagocytosis by Sertoli cells.

Footnotes

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↵* This work was supported in part by a grant-in-aid for scientific research from the Ministry of Education, Science and Culture of Japan. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PS

phosphatidylserine

FITC

fluorescein isothiocyanate

PC

phosphatidylcholine

PI

phosphatidylinositol.
↵² H. Ando, T. Koji, and Y. Nakanishi, unpublished observations.
- Received July 1, 1996.
- Revision received September 17, 1996.