The assembly of the major desmosome glycoproteins of Madin-Darby canine kidney cells.
Madin-Darby canine kidney (MDCK) cells are unable to form desmosomes when cultured in low-calcium medium [( Ca2+] less than 0.1 meq./l), but can be induced to do so by raising the calcium to physiological concentrations (1-2 meq./l). We have previously demonstrated that this block correlated with increased desmosomal protein turnover. Here we have immunoprecipitated the major desmosome glycoproteins [DGI (150 kDa) and DGII/III (120/100 kDa)] from non-ionic detergent-soluble and -insoluble fractions prepared from metabolically labelled MDCK cells cultured in standard or low-calcium medium. Pulse-chase studies showed that both DGI and DGII/III became unextractable in non-ionic detergent before their arrival at the cell surface, whether cells were grown in standard or low-calcium medium. The non-ionic detergent insolubility of these membrane components is therefore a separate step which precedes the formation of morphologically recognisable desmosomes.
Penn
E J
EJ
National Institute for Medical Research, London, England.
Hobson
C
C
Rees
D A
DA
Magee
A I
AI
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D003896:Desmosomes / Q000378:metabolism*; D004285:Dogs; D004705:Endocytosis; D006023:Glycoproteins / Q000096:biosynthesis*; D007163:Immunosorbent Techniques; D007668:Kidney / Q000187:drug effects / Q000648:ultrastructure*; D012995:Solubility
D006023:Glycoproteins; D002118:Calcium