Proteasome (prosome) subunit variations during the differentiation of myeloid U937 cells
Titel:
Proteasome (prosome) subunit variations during the differentiation of myeloid U937 cells
Auteur:
Laurent Henry Ahsene Baz Marie-Thérèse Château René Caravano Klaus Scherrer Jean Paul Bureau
Verschenen in:
Analytical cellular pathology
Paginering:
Jaargang 15 (2001) nr. 3 pagina's 131-144
Jaar:
2001-04-01
Inhoud:
20S proteasomes (prosomes/multicatalytic proteinase) are protein particles built of 28 subunits in variable composition. We studied the changes in proteasome subunit composition during the differentiation of U937 cells induced by phorbol-myristate-acetate or retinoic acid plus 1,25-dihydroxy-cholecalciferol by western blot, flow cytometry and immuno-fluorescence. p25K (C3), p27K (IOTA) and p30/33K (C2) subunits were detected in both the nucleus and cytoplasm of undifferentiated cells. Flow cytometry demonstrated a biphasic decrease in proteasome subunits detection during differentiation induced by RA+VD. PMA caused an early transient decrease in these subunits followed by a return to their control level, except for p30/33K, which remained low. Immuno-fluorescence also showed differences in the cytolocalization of the subunits, with a particular decrease in antigen labeling in the nucleus of RA+VD-induced cells, and a scattering in the cytoplasm and a reorganization in the nucleus of PMA-induced cells. Small amounts of proteasomal proteins were seen on the outer membrane of non-induced cells; these membrane proteins disappeared when treated with RA+VD, whereas some increased on PMA-induced cells. The differential changes in the distribution and type of proteasomes in RA+VD and PMA-induced cells indicate that, possibly, 20S proteasomes may play a role in relation to the mechanisms of differentiation and the inducer used.