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Abstract. We have examined the immunocytochemical localization of protein kinase C (PKC) in NIH 3T3 cells using mAbs that recognize Type 3 PKC. In control cells, the immunofluorescent staining was similar with mAbs directed to either the catalytic or the regulatory domain of PKC. Type 3 PKC localized in a diffuse cytoplasmic pattern, while the nuclei were apparently unstained. Cytoskeletal components also were stained. Treatment of the cells with phorbol 12-myristate 13-acetate (PMA) resulted in a redistribution of PKC with a specific increase in nuclear PKC. Compared to control cells, the staining with the anticatalytic domain mAbs changed markedly, covering the entire cell surface. In contrast, the staining by the antiregulatory domain mAb did not cover the cell surface and the nuclei remained unstained; these results suggest that PKC activation leads to a conformational change of the regulatory domain such that the epitope recognized by the antiregulatory domain mAb is not readily accessible.We have demonstrated by three criteria that PMA treatment specifically increased PKC in the nucleus: (a) immunofluorescent staining in isolated nuclei increased; (b) Western blots showed that our mAbs detected only one protein, the 82-kD PKC, whose level increased in nuclear lysates from PMA-treated cells; and (c) PKC activity increased in nuclear lysates. In fractionation studies we demonstrated that PKC specifically localized to the nuclear envelope fraction. These results demonstrate that PMA activation leads to a rapid redistribution of Type 3 PKC to the nuclear envelope, and suggests that this isozyme may play a role in mediating PKC-induced changes in gene expression.p ROTEIN kinase C (PKC)' is involved in the regulation of many cellular processes, including differentiation, hormone and neurotransmitter release, and gene activation. Cloning studies have demonstrated that PKC is a family of closely related genes which encode a number of isozymes. Initially, three different PKC genes (or,/3, 3") were found; additional cDNA clones (tS, e, ~') have subsequently 1. Abbreviations used in this paper: PBA, PBS containing 1% BSA; PDBu, phorbol dibutyrate; PKC, protein kinase C; PMA, phorbol 12-myristate 13-acetate.2. We were unable to precisely assess the percent of total PKC activity represented in the nuclear fraction after PMA treatment of the cells. We observed in seven experiments that the total picomoles of PKC activity recovered from the PMA-treated cells was only 50-70% of the total activity from the control cells. This was not due to incomplete extraction of PKC membrane activity from PMA-treated cells, since we verified by immunoblotting that our NP-40 extraction procedure removed all the immunoreactive Type 3 PKC from the membrane fractions (data not shown). PMA treatment did not alter the migration of PKC on the DEAE columns, since elution of the columns with increasing NaCI concentrations did not improve the recovery of PKC. Furthermore, immunoblots did not reveal the presence of PKC fragments. This indicates th...

The tetracycline analogs minocycline and doxycycline are inhibitors of metalloproteinases (MMPs) and have been shown to inhibit angiogenesis in vivo. To further study the mechanism of action of these compounds we tested them in an in vitro model of angiogenesis: aortic sprouting in fibrin gels. Angiogenesis was quantitated in this system by a unique application of planar morphometry. Both compounds were found to potently inhibit angiogenesis in this model. To further characterize the activity of these compounds against MMPs, we determined the IC50S of both compounds against representatives of three classes of metalloproteinases: fibroblast collagenase, stromelysin, and gelatinase A. Doxycycline was found to inhibit collagenase, gelatinase A and stromelysin with IC50S of 452 microM, 56 microM and 32 microM, respectively. Minocycline was found to inhibit only stromelysin in the micromolar range with an IC50 of 290 microM. Since these results suggest that these compounds may not have been inhibiting in vitro angiogenesis by an MMP-dependent mechanism, we decided to test the effects of the potent MMP inhibitor BB-94. This compound failed to inhibit aortic sprouting in fibrin gels, thus strongly suggesting that both doxycycline and minocycline act by an MMP-independent mechanism. These results have implications for the mechanism of action of tetracycline analogs, particularly where they are being considered for the treatment of disorders of extracellular matrix degradation including periodontal disease, arthritis, and tumor angiogenesis.

Gap junctions coordinate electrical signals and facilitate metabolic synchronization between cells. In this study, the authors have developed a novel assay for the identification of gap junction blockers using fluorescence microscopy imaging-based high-content screening technology. In the assay, the communication between neighboring cells through gap junctions was measured by following the redistribution of a fluorescent marker. The movement of calcein dye from dye-loaded donor cells to dye-free acceptor cells through gap junctions overexpressed on cell surface membranes was monitored using automated fluorescence microscopy imaging in a high-throughput compatible format. The fluorescence imaging technology consisted of automated focusing, image acquisition, image processing, and data mining. The authors have successfully performed a high-throughput screening of a 486,000-compound program with this assay, and they were able to identify false positives without additional experiments. Selective and pharmacologically interesting compounds were identified for further optimization. (Journal of Biomolecular Screening 2003:489-499)

BackgroundLarge-scale expansion of myogenic progenitors is necessary to support the development of high-throughput cellular assays in vitro and to advance genetic engineering approaches necessary to develop cellular therapies for rare muscle diseases. However, optimization has not been performed in order to maintain the differentiation capacity of myogenic cells undergoing long-term cell culture. Multiple extracellular matrices have been utilized for myogenic cell studies, but it remains unclear how different matrices influence long-term myogenic activity in culture. To address this challenge, we have evaluated multiple extracellular matrices in myogenic studies over long-term expansion.MethodsWe evaluated the consequence of propagating mouse and human myogenic stem cell progenitors on various extracellular matrices to determine if they could enhance long-term myogenic potential. For the first time reported, we comprehensively examine the effect of physiologically relevant laminins, laminin 211 and laminin 521, compared to traditionally utilized ECMs (e.g., laminin 111, gelatin, and Matrigel) to assess their capacity to preserve myogenic differentiation potential.ResultsLaminin 521 supported increased proliferation in early phases of expansion and was the only substrate facilitating high-level fusion following eight passages in mouse myoblast cell cultures. In human myoblast cell cultures, laminin 521 supported increased proliferation during expansion and superior differentiation with myotube hypertrophy. Counterintuitively however, laminin 211, the native laminin isoform in resting skeletal muscle, resulted in low proliferation and poor differentiation in mouse and human cultures. Matrigel performed excellent in short-term mouse studies but showed high amounts of variability following long-term expansion.ConclusionsThese results demonstrate laminin 521 is a superior substrate for both short-term and long-term myogenic cell culture applications compared to other commonly utilized substrates. Since Matrigel cannot be used for clinical applications, we propose that laminin 521 could possibly be employed in the future to provide myoblasts for cellular therapy directed clinical studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13395-016-0116-4) contains supplementary material, which is available to authorized users.