Temporal analysis of connexin43 protein and gene expression throughout the menstrual cycle in human endometrium.

OBJECTIVE: To analyze the pattern of connexin43 gene and protein expression in human endometrium throughout the menstrual cycle. DESIGN: Controlled clinical study. SETTING: An academic research center. PATIENT(S): Women with 28-day menstrual cycles who had mechanical infertility and failed to conceive after IVF treatment. INTERVENTION(S): Endometrial and blood samples were collected on days 8, 12, 14, 21, and 25 of spontaneous menstrual cycles. MAIN OUTCOME MEASURE(S): Endometrial expression of connexin43 protein and messenger RNA, endometrial thickness, and serum concentrations of gonadotropins and steroids. RESULT(S): The expression of connexin43 gene and protein decreased on day 12 and day 14 of the menstrual cycle and then increased on day 21 and day 25, respectively. A serum LH surge accompanied by a peak in the FSH concentration was observed on days 12-14. The progesterone concentration increased on days 21-25, but there was no significant change in the E2 concentration. The thickness of the endometrium increased between days 8 and 12 and did not change further between days 21 and 25. CONCLUSION(S): The expression of connexin43 gene and protein in human endometrium changes during the menstrual cycle in a pattern that is associated with the secretion of LH, FSH, and progesterone. This pattern may serve as a marker for implantation competence.

Linking protein kinase C to the cell cycle: ectopic expression of PKC eta in NIH3T3 cells alters the expression of cyclins and Cdk inhibitors and induces adipogenesis.

Protein kinase C encodes a family of enzymes implicated in cellular differentiation, growth control and tumor promotion. However, very little is known with respect to the molecular mechanisms that link protein kinase C to cell cycle control. Here we report that ectopic expression of PKC eta in NIH3T3 fibroblasts blocks the normal phosphorylation of the Rb protein in quiescent cultures restimulated to enter the cell cycle; PKC eta activates a cellular program that includes increased expression of cyclins E (but not cyclin D), as well as the induced expression of the cyclin-dependent kinase inhibitors p21WAF1 and p27KIP1. The increased expression of the latter inhibitors and their association with the cyclin E-Cdk2 complex results in decreased cyclin E associated kinase activity. Furthermore, in contrast to the control NIH3T3 cells, the cell that express PKC eta can be induced to undergo adipocyte differentiation in response to adipogenic hormones. Thus, PKC eta induces altered expression of several cell cycle related functions, which may contribute to its ability to promote cellular differentiation.

The relationship between ejaculated ram sperm mitochondrial protein synthesis and motility.

D-chloramphenicol, at concentrations of 20 and 40 micrograms/ml, inhibited over 80% of the newly synthesized mitochondrial proteins expressed by incorporation of 3H-amino acid mixture. At concentrations of 20 and 40 micrograms ml-1, D-chloramphenicol enhanced the collective motility of washed ram spermatozoa. The collective motility measured by the multichannel Reflectospermiograph system, significantly enhanced the motility wave frequencies and amplitudes by 24-17% and 65-32%, respectively. Furthermore, the longevity of the collective motility was prolonged by 12-19%. In about 20% of the cases, when the original sperm motility was low, it was found that 40 micrograms ml-1 D-chloramphenicol has maximum stimulation effect on sperm motility in inverse fashion. Since the mitochondria are located adjacent to the motility initiation area, it can be speculated that the mitochondrial protein(s) directly inhibiting the axonemal-ATPase activity or indirectly blocking sperm metabolite, are essential for maintaining sperm motility.

The protein kinase C-related PKC-L(eta) gene product is localized in the cell nucleus.

The tumor promoters phorbol esters are thought to induce changes in cell growth and gene expression by direct activation of protein kinase C (PKC). However, the molecular mechanisms by which PKC molecules transduce signals into the cell nucleus are unknown. In this study, we provide evidence for a direct target for phorbol esters in the nucleus. We demonstrate that the new PKC-related family member, PKC-L, recently isolated by us, is expressed specifically in the cell nucleus. Localization of PKC-L in the cell nucleus is shown both by immunofluorescence staining and by subcellular fractionation experiments of several human cell lines, including the human epidermoid carcinoma line A431. Treatment of these cells by phorbol esters does not induce the down-regulation of PKC-L, in contrast to their effect on classical PKC family members. This is the only PKC isoenzyme described so far that resides permanently and specifically in the cell nucleus. PKC-L may function as an important link in tumor promoting, e.g., as a nuclear regulator of gene expression that changes the phosphorylation state of transcriptional components such as the AP-1 complex.