Gonadotropins were recently demonstrated to be able to activate the MAPK cascade, but the physiological significance of this activation is still obscure. In the present work we demonstrate that highly luteinized human granulosa cells obtained from in vitro fertilization patients respond to human LH as well as to forskolin in phosphorylation of extracellular-signal regulated kinases 1 and 2 (ERK1 and -2). Moreover, the potent MAPK inhibitors, PD98059 and UO126, augment progesterone production in these cell cultures concomitantly with specific elevation of intracellular steroidogenic acute regulatory protein (StAR). Intracellular levels of the cytochrome P450 side-chain cleavage enzyme system do not seem to be affected. Similar observations were made with rat preovulatory or preantral granulosa cells stimulated with LH, FSH, or forskolin. Elevation of StAR expression by the MAPK inhibitors involved elevation of StAR mRNA, as demonstrated by RT-PCR in the human cells. Immunocytochemical studies using specific antibodies to StAR demonstrate a higher content of mitochondrial StAR in control as well as in gonadotropin-stimulated cells in the presence of PD98059 compared with cells not treated with PD98059. The cultured cells express the transcription factor steroidogenic factor-1 (SF-1), the phosphorylation of which is known to activate the expression of StAR, as well as dosage-sensitive sex reversal adrenal hypoplasia congenita, critical region on the X chromosome gene-1 (DAX-1), which is known to negate SF-1 activity. Intracellular levels of DAX-1 decreased significantly during 24 h of incubation of cells with or without LH in the presence of PD98059 or UO126 compared with those in cultures incubated in the absence of the MAPK inhibitors. The expression of SF-1 was suppressed by LH, whereas MAPK inhibitor could block this effect and further elevate SF-1 levels. Thus, activation of the MAPK cascade by gonadotropins may serve as a novel mechanism to down-regulate steroidogenesis via attenuation of StAR expression. Moreover, modulation of DAX-1 and SF-1 intracellular levels in these cells suggests that these transcription factors could be involved in MAPK suppression of StAR expression.

The synthesis and characterization of novel core-shell macromolecules consisting of a fluorescent perylene-3,4,9,10-tetracarboxdiimide chromophore in the center surrounded by a hydrophobic polyphenylene shell as a first and a flexible hydrophilic polymer shell as a second layer was presented. Following this strategy, several macromolecules bearing varying polymer chain lengths, different polymer shell densities, and increasing numbers of positive and negative charges were achieved. Because all of these macromolecules reveal a good water solubility, their ability to cross cellular membranes was investigated. In this way, a qualitative relationship between the molecular architecture of these macromolecules and the biological response was established.

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A new esterase gene from thermophilic bacteria Ureibacillus thermosphaericus was cloned into the pET32b vector and expressed in Escherichia coli BL21(DE3). Alignment of the estUT1 amino acid sequence revealed the presence of a novel canonical pentapeptide (GVSLG) and 41-47% identity to the closest family of the bacterial lipases XIII. Thus the esterase estUT1 from U. thermosphaericus was assigned as a member of the novel family XVIII. It also showed a strong activity toward short-chain esters (C2-C8), with the highest activity for C2. When p-nitrophenyl butyrate is used as a substrate, the temperature and pH optimum of the enzyme were 70-80 °C and 8.0, respectively. EstUT1 showed high thermostability and 68.9 ± 2.5% residual activity after incubation at 70 °C for 6 h. Homology modeling of the enzyme structure showed the presence of a putative catalytic triad Ser93, Asp192, and His222. The activity of estUT1 was inhibited by PMSF, suggesting that the serine residue is involved in the catalytic activity of the enzyme. The purified enzyme exhibited high stability in organic solvents. EstUT1 retained 85.8 ± 2.4% residual activity in 30% methanol at 50 °C for 6 h. Stability at high temperature and tolerance to organic solvents make estUT1 a promising enzyme for biotechnology application.