MRP8 and MRP14, S-100-like proteins associated with myeloid differentiation, are translocated to plasma membrane and intermediate filaments in a calcium-dependent manner

MRP8 and MRP14 are two Ca(2+)-binding proteins of the S-100 family expressed by myelomonocytic cells. Both proteins assemble to noncovalently associated complexes in a Ca(2+)-dependent manner. Members of the S-100 family are known to play a role in cytoskeletal- membrane interactions; therefore, we investigated the subcellular distribution of MRP8/MRP14 and their complexes in human monocytes. Using differential centrifugation and subsequent Western blot or enzyme- linked immunosorbent assay analysis, we found that MRP8/MRP14 were almost completely translocated from the cytoplasma to membrane and cytoskeletal structures in a Ca(2+)-dependent manner. Using a cross- linking technique, complexed forms of MRP8/MRP14 were found to be associated with the plasma membrane. Analysis of MRP-transfected L132 cells showed that the MRP8 as well as the MRP14 component of the MRP8/MRP14 complex may independently bind to membrane and cytoskeletal structures. Furthermore, immunogold electron microscopy showed a colocalization of MRP8/MRP14 and the intermediate filament type III protein vimentin in A23187-treated monocytes. Our data indicate that, in analogy to other S-100-like proteins, MRP8 and MRP14 play a role in Ca(2+)-dependent cytoskeletal-membrane interactions. Restriction of MRP8/MRP14 expression to distinct stages of myelomonocytic differentiation suggests that these proteins are involved in highly specific pathways of intracellular signaling in phagocytes.     

Down-regulation of tenascin expression by antiprogestins during terminal differentiation of rat mammary tumors.

Studies on tenascin expression in hormonally dependent growing tissues of breast and endometrium suggested that its expression parallels the progression of normal or malignant proliferative alteration of the tissue. With the study presented here we addressed the question of whether antiprogestin-induced terminal differentiation down-regulates tenascin expression. By comparative immunolocalization of tenascin in sections of untreated 7,12-dimethylbenz[alpha]anthracene-induced tumors, tumors grown in ovariectomized animals, tamoxifen-treated tumors, and antiprogestin-treated tumors, we obtained the following results. (a) The entire extracellular space of the stromal mesenchyme was filled by tenascin immunoreactivity in cases of untreated control tumors. (b) Both ovariectomy and antiestrogen treatment with tamoxifen did not affect the overall staining pattern and resulted in a slight increase of the arbitrarily judged staining intensity. (c) Within antiprogestin-treated tumors tenascin-like immunoreactivity predominantly was restricted to fiber-like, collagenous connective tissue structures, which appeared in the stromal compartment as a result of the antiprogestin treatment. In large areas of the tumor composed of apparently secretory active tumor cells we failed to immunolocalize tenascin. Our results provide further evidence that expression of tenascin reflects both benign and malignant proliferative alterations of the tissue, whereas its down-regulation is correlated to differentiation of the tissue. Additionally, evidence is provided that the mechanism of tumor growth inhibition by antiprogestins indeed is induction of terminal differentiation of tumor cells.     

Does the single-breath N2 test identify the smoker who will develop chronic airflow limitation?

We report here the results of a 9- to 11-yr follow-up of 2 cohorts in which spirometry and the single-breath N2 test were used throughout the follow-up period to determine the usefulness of the single-breath N2 test in identifying the smoker who is experiencing a rapid decline in FEV1 and is therefore likely to be at risk of developing chronic airflow limitation. The analyses are based on 734 subjects tested from 3 to 5 times over the follow-up period; 82 smokers developed an abnormal FEV1 during the follow-up period. Of these, 71 (87%) had had an abnormal single-breath N2 test at some time prior to the FEV1 becoming abnormal. Of the single-breath N2 test variables, CC/TLC was the only one significantly associated with the rate of decline of FEV1 in both cohorts once adjustments were made for age, sex, height, and smoking. We conclude that the single-breath N2 test can be useful in identifying the smoker who is at risk of developing chronic airflow limitation. However, its usefulness is diminished by the high proportion of smokers who have mild functional abnormalities but do not progress to develop chronic airflow limitation. We also find that the single-breath N2 test does not appear to have a useful predictive value in nonsmokers.