Two-dimensional gel electrophoresis of 125I-labeled surface proteins of human fibroblasts

New plasma membrane proteins expressed by a high metastatic variant of a chemically induced tumor

The composition of plasma membrane proteins of related low and high metastatic tumor cells were compared in order to elucidate possible genetic changes which may occur during progression of tumor cells towards metastatic capacity. For this purpose a procedure was worked out which allows the purification of mouse plasma membrane (PM) proteins from biosynthetically labeled cells. PM isolated from the two related T lymphoma lines Eb and ESb, which differ greatly in metastatic capacity, as well as from Con A-activated T cell blasts displayed similar degrees of purification as shown by marker enzyme analysis. When [35S]-methionine-labeled proteins of such PM preparations from cloned Eb and ESb cells were compared by 2-D gel electrophoresis it was found that maps of the highly metastatic variant ESb cells permitted detection of about 50 new protein spots which were not found on the 2-D gel maps of the parental Eb cells. Approximately 80% of these new spots were also found on maps derived from syngeneic splenic Con A blasts. This observation indicated that most of the newly expressed membrane proteins of ESb cells were possible differentiation or cell activation-related and not tumor cell-specific.

Computer applications in analysis, mapping and cataloging of proteins separated by two dimensional electrophoresis

Two dimensional electrophoretic separation of complex mixtures of proteins can only be exploited to its fullest potential using sophisticated computerized spot detection, quantification, pattern recognition, pattern normalization, data reduction and data storage. We present a discussion of some of the technical problems and of the options available which will ultimately lead toward full computerization of the data.

Two-dimensinal gel electrophoresis of rat liver nuclear washes, nuclear matrix, and hnRNA proteins

The proteins of rat liver cytoplasm, nuclear washes, matrix, membrane, heterogeneous nuclear (hn)RNA proteins and chromatin were examined by two-dimensional gel electrophoresis. The inclusion in the gels of six common protein standards of carefully selected molecular weight and isoelectric point allowed us to clearly follow the distribution of specific proteins during nuclear extraction. In the nuclear washes and chromatin, we observed five classes of proteins: (a) Exclusively cytoplasmic proteins, present in the first saline-EDTA wash but rapidly disappearing from subsequent washes; (b) ubiquitous proteins of 75,000, 68,000, 57,000, and 43,000 mol wt, the latter being actin, found in the cytoplasm, all nuclear washes and the final chromatin pellet; (c) proteins of 94,000, 25,000, and 20,500 mol wt specific to the nuclear washes; (d) proteins present in the nuclear washes and final chromatin, represented by species at 62,000, 55,000, 54,000, and 48,000 mol wt, primarily derived from the nuclear matrix; and (e) two proteins of 68,000 mol wt present only in the final chromatin. The major 65,000-75,000-mol wt proteins seen by one-dimensional gel electrophoresis of nuclear matrix were very heterogeneous and contained a major acidic, an intermediate, and a basic group. A single 68,000-mol wt polypeptide constituted the majority of the membrane-lamina fraction, consistent with immunological studies indicating that a distinct subset of matrix proteins occurs, associated with heterochromatin, at the periphery of the nucleus. Actin was the second major nuclear membrane-lamina protein. Two polypeptides at 36,000 and 34,000 mol wt constituted 60% of the hnRNP. Approximately 80% of the mass of the nonhistone chromosomal proteins (NHP) from unwashed nuclei is contributed by nuclear matrix and hnRNPs, and essentially the same patterns were seen with chromatin NHP. The concept of NHP being a distinct set of DNA-bound proteins is unnecessarily limiting. Many are derived from the nuclear matrix or hnRNp particles and vary in the degree to which they share different intracellular compartments.