Jette B. Lauridsen

Short‐term culturing of low‐grade superficial bladder transitional cell carcinomas leads to changes in the expression levels of several proteins involved in key cellular activities

Fresh, superficial transitional cell carcinomas (TCCs) of low‐grade atypia (3 grade I, Ta; 6 grade II, Ta), as well as primary cultures derived from them were labeled with [35S]methionine for 16 h, between 2 and 6 days after inoculation. Whole protein extracts were subjected to IEF (isoelectric focusing) two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) followed by autoradiography. Proteins were identified by a combination of proteomic technologies that included microsequencing, mass spectrometry, 2‐D PAGE immunoblotting and comparison with the bladder TCC protein database available on the internet (http://biobase.dk/cgi‐bin/celis). Comparison of the IEF 2‐D gel protein profiles of fresh tumors and their primary cultures showed that the overall expression profiles were strikingly similar, although differing significantly in the levels of several proteins whose rate of synthesis was differentially regulated in at least 85% of the tumor/culture pairs as a result of the short‐term culturing. Most of the proteins affected by culturing were upregulated and among them we identified components of the cytoskeleton (keratin 18, gelsolin and tropomyosin 3), a molecular chaperone (hsp 28), aldose reductase, GST π, metastasin, synuclein, the calreticulin precursor and three polypeptides of unknown identity. Only four major proteins were downregulated, and these included two fatty acid‐binding proteins (FABP:FABP5 and A‐FABP) which are thought to play a role in growth control, the differentiation‐associated keratin 20, and the calcium‐binding protein annexin V. Proteins that were differentially regulated in only some of the cultured tumors included alpha‐enolase, triosphosphate isomerase, members of the 14‐3‐3 family, hnRNPs F and H, PGDH, hsp (heat‐shock protein) 60, BIP, the interleukin‐1 receptor antagonist, the nucleolar protein B23, as well as several proteins of yet unknown identity. The suitability of in vitro bladder tumor culture models to study complex biological phenomena such as malignancy and invasion is discussed.

High-Resolution Two-Dimensional Gel Electrophoresis of Proteins: Isoelectric Focusing and Nonequilibrium pH Gradient Electrophoresis (NEPHGE)

Publisher Summary This chapter discusses high-resolution two-dimensional (2D) gel electrophoresis method. High-resolution two-dimensional (2D) gel electrophoresis is at present considered the method with the highest resolution for the separation of complex protein mixtures such as those present in eukaryotic cells. The technique, which separates proteins in terms of their isoelectric points and molecular weights, is commonly used to identify new cellular components for example cytoskeletal proteins, organelle components, etc., and to detect alterations in their expression using qualitative and quantitative comparisons. The method allows resolving proteins having apparent molecular weights between 8.5 and 230 kDa and pI values from 4 to 12.

Identification of a group of proteins that are strongly up‐regulated in total epidermal keratinocytes from psoriatic skin

Analysis using two‐dimensional (2D) gel electrophoresis of the [35S]‐methionine‐labelled proteins synthesized by non‐cultured total epidermal keratinocytes obtained from normal and psoriatic skin revealed 6 proteins that are strongly up‐regulated (5 times or more) in psoriatic skin. These proteins are synthesized at albeit lower levels by keratinocytes from normal and normal‐appearing (uninvolved) skin of psoriatic patients, and correspond to isoelectric focusing sample spot numbers 4311 (40.3 kDa), 4003 (12.4 kDa), 5008 (11.9 kDa), 3012 (11.6 kDa), 6016 (11.6 kDa) and 1015 (10;1 kDa) in the normal keratinocyte 2D gel protein database [Celis et al, (1990) Electrophoresis, in press]. These proteins are also detected in the labelling medium indicating that they are at least in part secreted. Given their striking regulatory behavior, these proteins may play a role in the pathogenesis of psoriasis.

Cell cycle-associated change in the expression of the proliferation-sensitive and heat-shock protein hs × 70 (IEF14): Increased synthesis during mitosis☆

The major heat-inducible protein of transformed human amnion cells (AMA) has been identified as the proliferation-sensitive polypeptide IEF14 (Mr 66 kDa; HeLa protein catalogue). From its mobility in two-dimensional gels (Mr and pI) as well as from the fact that this protein is immunoprecipitated by mAb C92 F3-5 (W. J. Welch, and J. P. Suhan, (1986) J. Cell Biol. 103, 2035-2052), we concluded that this polypeptide is either closely related or identical to the 72 kDa inducible stress human protein hs X 70 (H. R. B. Pelham (1986) Cell 46, 959-961). It is further shown that in AMA cells the rate of synthesis of this protein increases preferentially during mitosis. These results provide further evidence suggesting that the levels of hs X 70 can be modulated by mechanisms independent of heat shock.

Comprehensive, human cellular protein databases and their implication for the study of genome organization and function

Comprehensive, computerized databases of cellular protein information derived from the analysis of two‐dimensional gels, together with recently developed techniques to microsequence proteins offer a new dimension to the study of genome organization and function. In particular, human protein databases provide an ideal framework in which to focus the human genome sequencing effort.

Human proteins IEF 58 and 57a are associated with the Golgi apparatus.

A mouse monoclonal antibody (mAB 22‐II‐D8B) raised against lysed transformed human amnion cells (AMA) has been characterized. The mAB decorated the Golgi apparatus in growing and quiescent cultured monolayer cells (fibroblasts and epithelial cells) of various species as determined by double immunofluorescence labeling and colocalization with galactosyltransferase antibodies. It reacted with the acidic human proteins IEF 58 (M r = 29 000) and 57a, respectively (M r = 30 000) (HeLa protein catalogue number; [(1982) Clin. Chem. 28, 766]), Golgi staining was also observed in BS‐C‐1 cells microinjected with mAB 22‐II‐DSB suggesting that the epitopes recognized by the antibody are most likely located on the cytoplasmic face of the membranes. The precise localization of the antigens to the various cisternae of the Golgi apparatus could not be demonstrated by immunogold cytochemistry on ultrathin cryosections due to either weak reactivity of the antibody or low concentration of the antigens. Immunofluorescence staining with mAB 22‐II‐D8B of lymphoid human Molt‐4 cells and some human tissues failed to reveal any significant staining even though these expressed high levels of both IEF 58 and 57a. These results are taken to imply that the epitopes recognized by mAB 22‐II‐D8B may be masked in some cell types.