The cytoskeletal protein vinculin, a putative actin -plasma-membrane linker, has been shown by hydrophobic photo-labeling to interact in vitro directly with bilayers of acidic phospholipids [Niggli et al. (1986) J. B i d . Chem. 261, 6912-69181. In order to demonstrate that such an interaction occurs also in intact cells, chicken embryo fibroblasts were incubated for 2 h with a 3H-labeled photoactivatable fatty acid, 11-(4-[3-(trifluoromethyl)diazirinyl]phenyl)-[2-"H]undecanoic acid. This resulted in biosynthetic incorporation into cellular lipids of a fraction of the fatty acid added. Following photolysis, vinculin was immunoprecipitated from different subcellular fractions using a specific polyclonal anti-vinculin antibody. The protein was recovered from both the cytosolic and the crude membrane fraction. Vinculin from both fractions incorporated label, but the membrane-associated population was at least eight times more strongly photolabeled than the cytosolic protein. Moreover, photolysis increased only labeling of the membrane-bound but not of the cytosolic protein. These results suggest that the direct interaction of vinculin with the hydrophobic core of the phospholipid layer observed in vitro may also be relevant in intact cells, and may be involved in its function as a linker protein.The widely distributed protein vinculin has been suggested to participate in actin-filament -plasma-membrane linkage. This hypothesis is mainly based on the highly specific location of vinculin in areas where this linkage occurs [l]. However, conclusive evidence confirming this hypothesis is still lacking and the molecular mechanism of the proposed linkage of vinculin to both actin filaments and the plasma membrane has not yet been clarified. Recent experiments suggest very complex interactions. Besides vinculin, the proteins talin and a-actinin are also components of areas of plasma-membraneactin attachment, such as for instance focal contacts, areas of closest contact between cultured cells and the substrate. Vinculin has been shown to interact in vitro both with talk [2] and with a-actinin [3]. Only the latter protein has conclusively been shown also to interact with actin [4]. Talin itself binds in vitro to the purified transmembrane fibronectin receptor [5]. Talin, vinculin and a-actinin may therefore constitute a chain of attachment from the plasma membrane to the actin filaments. However, such a complex has not yet been demonstrated to occur in situ. A different mechanism may be operative in adherens junctions, where only vinculin, but not talin, is present [6].Not only proteins, but also lipids may play a role in the interaction of vinculin with membranes. Vinculin has been shown to interact in vitro with acidic phospholipids [7] and, using a photoactivatable phospholipid, to insert into the hydrophobic core of liposome bilayers [8]. This insertion is critically dependent on the presence of acidic phospholipids and occurs at physiological salt and phospholipid concentrations, although it is maximal at low ionic str...
The influence of experimental streptozotozin-induced diabetes on hepatic drug metabolism in vivo has been studied in rats, using 14CO2-exhalation after 14C-aminopyrine injection. Male diabetic rats showed a decreased (-18%), females an increased (+19%) 14CO2-exhalation compared to controls, indicating altered hepatic drug metabolism due to diabetes.
Die griine Queel~ilberlinie wurde mit einem hoehauflSsenden Interferenzapparat untersueht. Die beobaehtete Struktur steht im Widersprueh zu der Annahme eines Kernmoments J ~ 1 mit kleinem ma~etisehen Moment fOx die geradzahlige Hg-Isotope 198. Es ~st wahrseheinlieh ebenso wie bei Hg2o4, Hg20~, Hg2o o gleieh Null. Die als Testlinie bekannte griine Quecksilberlinie wurde zur Priifung der Leistungsf~higkeit eines hoehauflSsenden Spektralapparates benutzt. Der Apparat war ein Multiplex-]nterferometer naeh Gehreke und Laul), welches yon der Firma Halle Nachf., Berlin-Steglitz, freundliehst zur Verfagung gestellt wurde. Die eine Quarzplatte war 17 mm dick, die andere 25 ram. Es kam darauf an, die ,,Nullinie" von 2 5461, die bekanntlich aus eng benaehbarten Hyperfeinstrukturkomponenten besteht, mSgliehst v011st~ndig aufzulSsen.Zur Erzeugung der grfmen Linie wrLrden versehiedene Entladungsformen verwendet, die positive Lichts~ule im Geil3]errohr und die Hohlkathoden-Glimmentladung. Die RShrenspannung betrug einige hundert Volt, die Stromst~rke im Gei~lerrohr 50 mA, im Hohlkathodenrohr 150 mA. Das Geil~ierrohr war entweder ungekiihlt oder wassergekahlt, das Hohlkathodenrohr war wassergekiihlt oder mit flfissiger Luft gekiihlt. Die grane Linie wurde mittels eines l~onochromators gus dem Spektrum ausgesondert und dem Intefferenzvorgang unterwoffen. Beobachtet wurde visuell und photographiseh. Bei visueller Beobachtung erschienen die Komponenten wesentlieh sch~rfer als bei photographiseher Beobachtung, weft bei visueller Beobachtung der Temperatuxeffekt wegfiel, der bei photographiseher Beobaehtung infolge tier Belichtungsdauer Unseh~rfen hervorrief. Die Aufnahmen der ttyperfeinstruktur der Nullinie mit. ungekiihltem und gekiihltem Geil31errohr end off und end on zeigten tmtereinander ~hnliehe Intensit~tsverteilung, ebenso die s mit wassergekahltem und mit flassiger Luft gekiihltem ttohlkathodenrohr. Deshalb ist bier nur je eine vergrSl3erte AuJ:nahme mit dem GeiBlerrohr und dem Hohl-1) E.
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