Manganese-dependent cell-substratum adhesion

In the presence of manganese, baby hamster kidney cells attached and spread on substrata without added adhesion factors (e.g., fibronectin, lectins). This Mn-dependent adhesion occurred even when the substratum was coated with proteins, such as albumin, haemoglobin, immunoglobulin or ovalbumin, or a dried collagen film. Under similar conditions, cells without Mn in Mg/Ca-containing medium attached poorly and did not spread. Other divalent cations, including Mg, Ca, Fe, Co and Ni, could not replace Mn. Cell surface sites required for Mn-dependent adhesion were destroyed by brief proteolytic treatment of the cells with trypsin or Pronase under conditions where the fibronectin-receptor was unaffected. Also, addition to the incubations of antibodies that inhibited ligand-mediated cell adhesion (e.g., by fibronectin or lectins) inhibited adhesion of cells in Mn-containing medium and caused rounding of cells previously attached and spread in the presence of Mn. The continuous presence of Mn was required for adhesion. That is, cells that were attached and spread in Mn-containing medium and then switched to Mg/Ca-containing medium (which permitted cytoskeletal function) were found to round up and detach. In marked contrast, cells that were allowed to attach and spread on fibronectin-coated substrata in the presence of Mn did not round up when they were switched to Mg/Ca containing medium. Possible explanations for Mn-dependent cell adhesion are discussed.