Naslov
Lanosterol metabolism and sterol regulatory element binding protein (SREBP) expression in male germ cell maturation

Autori
Fon Tacer, Klementina ; Kalanj-Bognar, Svjetlana ; Waterman, Michael ; Rozman, Damjana

Izvornik
Journal of Steroid Biochemistry and Molecular Biology (0960-0760) 85 (2003), 2-5; 429-438

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
cholesterol; SREBP; testis; male germ cell; MAS

Sažetak
Expression of genes involved in cholesterol biosynhtesis in male germ cells is insensitive to the negative cholesterol feedback regulation, in contrast to cholesterol level-sensitive/sterol regulatory element binding protein (SREBP)-dependent gene regulation in somatic cells. The role of sterol regulatory element binding proteins in spermatogenic cells was an enigma until recently, when a soluble, 55 kDa cholesterol-insensitive form of SREBP2 (SREBP2gc) was discovered (Mol Cell Endocrinol 22, 2002:8478), being translated from a germ cell-specific SREBP2 mRNA. Our RT-PCR results also show that SREBP2 as well as SREBP1c mRNAs are detectable in prepubertal and postpubertal male germ cells while SREPB1a is not detected. Surprisingly, three SREBP2 immunoreactive proteins (72, 63 and 55 kDa), that are not present in mouse liver nuclei, reside in testis nuclei of prepubertal and adult mice. The 55 kDa protein is likely SREBP2gc, the other two isoforms are novel. HPLC measurements in liver and testes of fasted prepubertal and postpubertal mice showed no significant difference in cholesterol level. However, FF-MAS and lanosterol/testis-meiosis activating sterol (T-MAS) intermediates that are detectable mainly in testes, increase in fasted postpubertal mice which coincides well with the elevated level of 68 kDa SREBP2. Similar to SREBP2gc, the two novel SREBP2 immunoreactive proteins seem to be insensitive to the level of cholesterol.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti, Kliničke medicinske znanosti

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