This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Passaniti, A. Articles by Hart, G. W. Search for Related Content PubMed PubMed Citation Articles by Passaniti, A. Articles by Hart, G. W.

Metastasis-associated Murine Melanoma Cell Surface Galactosyltransferase: Characterization of Enzyme Activity and Identification of the Major Surface Substrates¹

Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205

Surface galactosyltransferase (GT) has been described on a variety of cells where it is believed to be involved in cell-cell and cell-substratum adhesion. Here we show that B16 metastatic murine melanoma cells exhibit a 5-fold higher cell surface GT activity than their nonmetastatic counterparts, although total GT activity in NP-40 solubilized cells is similar for both melanoma variants. Interestingly, on living cells, this cell surface GT almost exclusively galactosylates an endogenous glycoprotein (M_r = 110,000). This metastasis-associated GT is specific for terminal D-N-acetylglucosamine, catalyzes the formation of a ß1–4 linkage, does not recognize polylactosaminoglycans, and has its specificity altered from D-N-acetylglucosamine to D-glucose by -lactalbumin; yet the M_r = 110,000 protein is not a major substrate when exogenous bovine GT is used on the outside of living cells.

In addition to this protein-specific endogenous GT activity, another cell surface GT activity that selectively galactosylates glucosylceramide is also prominent. Endogenous galactosylation of both protein and glycolipid substrates is reduced when the membrane is solubilized by the detergent NP-40 but remains unaltered in the presence of digitonin, which permeabilizes but does not dissolve the membrane. These data suggest that the GTs and their substrates are associated on the cell surface. Chloroquine treatment of intact cells leads to a 4-fold and a 3-fold increase in galactosylation of the M_r = 110,000 protein and glucosylceramide, respectively, suggesting that these two substrates normally reside mostly in the lysosomal or Golgi compartments. The increased expression of lysosomal membrane proteins on the surfaces of highly metastatic cells may, in part, also explain the galactosylation differences observed. These studies further suggest that increased surface localization of certain glycosyltransferases with highly restricted in situ substrate specificities may be a common feature of highly metastatic tumor cells.

¹ This work was supported by NIH Grant CA 42486 from the National Cancer Institute.

² Present address: National Institute on Aging. Gerontology Research Center, 4940 Eastern Avenue, Baltimore, MD 21224.

³ To whom requests for reprints should be addressed, at Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205.

Received 2/26/90. Accepted 8/20/90.

This article has been cited by other articles:

				X. Zhu, J. Jiang, H. Shen, H. Wang, H. Zong, Z. Li, Y. Yang, Z. Niu, W. Liu, X. Chen, et al. Elevated {beta}1,4-Galactosyltransferase I in Highly Metastatic Human Lung Cancer Cells: IDENTIFICATION OF E1AF AS IMPORTANT TRANSCRIPTION ACTIVATOR J. Biol. Chem., April 1, 2005; 280(13): 12503 - 12516. [Abstract] [Full Text] [PDF]

				T. Ogura, T. Noguchi, R. Murai-Takebe, T. Hosooka, N. Honma, and M. Kasuga Resistance of B16 Melanoma Cells to CD47-induced Negative Regulation of Motility as a Result of Aberrant N-Glycosylation of SHPS-1 J. Biol. Chem., April 2, 2004; 279(14): 13711 - 13720. [Abstract] [Full Text] [PDF]

				F. Johnson and B. Shur The level of cell surface beta1,4-galactosyltransferase I influences the invasive potential of murine melanoma cells J. Cell Sci., January 8, 1999; 112(16): 2785 - 2795. [Abstract] [PDF]