Isolation, characterization and molecular cloning of cathepsin D from lizard ovary: changes in enzyme activity and mRNA expression throughout ovarian cycle.
During vitellogenesis, the oocytes of oviparous species accumulate in the cytoplasm a large amount of proteic nutrients synthetized in the liver. Once incorporated into the oocytes, these nutrients, especially represented by vitellogenin (VTG) and very low-density lipoprotein (VLDL), are cleaved into a characteristic set of polypeptides forming yolk platelets. We have studied the molecular mechanisms involved in yolk formation in a reptilian species Podarcis sicula, a lizard characterized by a seasonal reproductive cycle. Our results demonstrate the existence in the lizard ovary of an aspartic proteinase having a maximal activity at acidic pH and a molecular mass of 40 kDa. The full-length aspartic proteinase cDNA produced from total RNA by RT-PCR is 1,442 base pairs long and encodes a protein of 403 amino acids. A comparison of the proteic sequence with aspartic proteinases from various sources demonstrates that the lizard enzyme is a cathepsin D. Lizard ovarian cathepsin D activity is maximal in June, in coincidence with vitellogenesis and ovulation, and is especially abundant in vitellogenic follicles and in eggs. Ovarian cathepsin D activity can be enhanced during the resting period by treatment with FSH in vivo. Northern blot analysis shows that cathepsin D mRNA is exceedingly abundant during the reproductive period, and accumulates preferentially in previtellogenic oocytes.
De Stasio
R
R
Dipartimento di Biologia Evolutiva e Comparata, Università Federico II, Naples, Italy.
Borrelli
L
L
Kille
P
P
Parisi
E
E
Filosa
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002402:Cathepsin D / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005260:Female; D015870:Gene Expression; D006066:Gonads; D006801:Humans; D008116:Lizards; D008969:Molecular Sequence Data; D010053:Ovary / Q000201:enzymology*; D012333:RNA, Messenger; D012098:Reproduction; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D012333:RNA, Messenger; D002402:Cathepsin D