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PubMed1977

Synthesis, secretion, and attachment of LETS glycoprotein in normal and transformed cells.

LETS glycoprotein is a surface glycoprotein which is absent or greatly diminished on the surfaces of transformed cells. Normal cells secrete large amounts of this protein into the medium; transformed cell medium contains much less. The difference is not due to degradation of the soluble LETS protein. Biosynthesis of LETS protein can be studied by analysis of cell extracts by detergent extraction and immune precipitation and appears to proceed in transformed cells at a reduced rate compared with normal cells. Addition of inhibitors of protein synthesis to transformed cell cultures causes the small amount of LETS protein in the medium to attach to the cells. Addition of normal conditioned medium, which contains LETS protein, to transformed cells alters their morphology towards normal. Addition of purified LETS protein to transformed cells causes the cells to attach, spread, align with one another, and regain actin cables. The results indicate that LETS protein can exchange between cell surface and medium and that it affects cellular adhesion, morphology, and cytoskeleton.

Adhesiveness↗

PubMed1977

Restoration of normal morphology, adhesion and cytoskeleton in transformed cells by addition of a transformation-sensitive surface protein.

Transformed cells lack a large, external, transformation-sensitive (LETS) glycoprotein which is a major surface component of their normal counterparts. Addition of LETS glycoprotein isolated from normal cells to transfomed cells restores certain morphological features and adhesive properties characteristic of normal cells. LETS protein is detected on the cell surface both by iodination using lactoperoxidase and by immunofluorescent staining. The surface distribution pattern detected by immunofluorescence is strikingly similar to that of normal cells. After addition of LETS protein, transformed cells also exhibit well defined actin cables which are not seen in untreated, transformed cells. All these alterations can be blocked by treating LETS protein with specific antisera or by subjecting it to mild trypsinization prior to addition to transformed cells. The effects are rapidly reversible by mild trypsinization, which removes the added LETS protein. The high rate of uptake of 2-deoxyglucose, characteristic of transformed cells, is not affected by LETS protein. These results suggest that LETS protein may have a role in cell attachment and spreading, and affect the organization of cytoskeleton.

Actins↗