Cyclic protein-2, a secretory product of rat Sertoli cells, is the proenzyme form of cathepsin L.
Previous studies demonstrated that secretion of Cyclic Protein-2 (CP-2) by mature rat Sertoli cells increased 30-fold from stage II to stages VI-VII of the cycle of the seminiferous epithelium and suggested that this protein was concentrated around compacted spermatids. Analysis of other organs revealed that CP-2 was also detectable in the epithelium of the proximal kidney tubule and in neurons originating from the supraoptic and paraventricular nuclei of the hypothalamus. We now have isolated a partial 1.8-kilobase (kb) cDNA for CP-2 mRNA, and sequence analysis revealed that CP-2 was the proenzyme form of the cysteine protease cathepsin L; this was corroborated by immunoprecipitation of CP-2 by anticathepsin L immunoglobulin G and by enzymatic analysis of purified CP-2. Northern analysis of testis mRNA revealed major (1.7 kb) and minor (2.2 kb) transcripts which differed in the length of their 3'-untranslated sequences. Low levels of CP-2/cathepsin L transcripts were detected in many organs, while high levels were only detected in testis, kidney, and liver. In seminiferous tubules, CP-2/cathepsin L mRNA was undetectable at stage II, increased to maximal levels at stages VI and VIIa,b, and was again undetectable at stage XII. At stages VI-VII, CP-2/cathepsin L mRNA was present in Sertoli but not germ cells. Taken together, these data suggest that CP-2/cathepsin L gene expression is regulated in a cell-specific manner and that in Sertoli cells this expression is influenced by germ cells at specific steps of development. We propose that at stages V-VII, secreted CP-2/cathepsin L degrades adhesion molecules which bind compacted spermatids to Sertoli cells, thereby facilitating movement of these spermatids toward the lumen of the tubule.
Erickson-Lawrence
M
M
Department of Population Dynamics, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205.
Zabludoff
S D
SD
Wright
W W
WW
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D056668:Cathepsin L; D002403:Cathepsins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D004247:DNA / Q000032:analysis / Q000235:genetics; D010450:Endopeptidases; D004792:Enzyme Precursors / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D007150:Immunohistochemistry; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D012708:Sertoli Cells / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
D004792:Enzyme Precursors; D012333:RNA, Messenger; D004247:DNA; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D056668:Cathepsin L; C534280:Ctsl protein, rat