TESTICULAR SPERMATOGENESIS, MORPHOGENESIS, AND GENE EXPRESSION
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(471) DIFFERENTIAL EXPRESSION AND LOCALIZATION OF ENDOSOMAL AND LYSOSOMAL PROTEINS DURING MAMMALIAN SPERMIOGENESIS.
Moreno, Ricardo1, 1 Department of Physiology, Santiago, CL
ABSTRACT- For many years the mammalian acrosome has been regarded as a modified lysosome since it contains both acrosomal and lysosomal enzymes, despite of the fact that the mature acrosome does not have any lysosomal marker. This controversy has motivated me to further investigate whether or not the mechanism of acrosome and lysosome share some components. Lysosomes are the endpoint of the endocityc and fagocityc route; in addition they received newly synthesized proteins and membranes from the Golgi apparatus. Each compartment has specific membrane bound markers making it possible to discern between early endosomes, late endosomes and lysosomes. Newly synthesized lysosomal proteins travel from the trans-Golgi to lysosomes in mannose-6-phospate receptor (M6PR) coated vesicles. Only in Cap phase spermatids the M6RP was present in the acrosome vesicle; M6PR had a cytoplasmic distribution in all the other differentiation steps. The transport of M6PRs from the TGN to endosomes is mediated by the multimeric complex AP-1. The distribution of gamma-adaptin, one of the subunits of the AP-1 complex, showed a punctate cytoplasmic distribution in pachytene spermatocytes and Golgi phase spermatids. No expression of this protein was detected in the ensuing differentiation steps. The lysosomal-associated membrane proteins (lamp) are specific for lysosomes in somatic cells. In mouse pachytene spermatocytes, lamp-2 label a number of dots throughout all the cytoplasm. This distribution remained the same in all the spermatid differentiation steps. On the other hand, lamp-2 was not detected in pachytene, or in Golgi or Cap phase spermatids. Lamp-1 transiently appeared in acrosome phase spermatids and labeled structures akin to lamp-2. None of them labeled the acrosome at any of the differentiation steps. Our results suggest that the expression of lamps are developmentally regulated during spermiogenesis and that the endocytic machinery that may contribute to the formation of the acrosome. Supported by DIPUC (2001/05E) and CONRAD (MFG-00-56).
KEY WORDS: spermatid, acrosome, lysosome, spermatozoa