Henry L, Baz A, Château M T, Scherrer K, Bureau J P
Laboratoire de Biologie Cellulaire et Cytogénétique Moléculaire (UPRES-JE 1952), Faculté de Médecine de Montpellier-Nîmes, Université Montpellier I, France.
Cell Prolif. 1996 Nov;29(11):589-607. doi: 10.1111/j.1365-2184.1996.tb00974.x.
Prosomes (Proteasomes/Multicatalytic proteinase (MCP)-complexes) are protein particles built of 28 subunits in variable composition, having proteinase activity. We have studied the changes in prosomal subunits p29K, p31K and the highly expressed p23K during the differentiation of U937 cells. Control cells had little prosomal subunit p31K in the cytoplasm, while p29K antigen was detected in both the nucleus and cytoplasm; more p23K antigen was found in the cytoplasm than in the nucleus. Flow cytometry demonstrated a biphasic intracellular decrease in prosomes during differentiation induced by phorbol-myristic-acetate (PMA) and retinoic acid plus 1,25-dihydroxycholecalciferol (RA + VD). p23K and p29K decreased both in the cytoplasm and the nucleus of differentiated cells, though the p23K antigen was concentrated near vesicles and the plasma membrane in PMA-induced cells. The p31K antigens disappeared from RA + VD-induced cells, while in PMA-induced cells, cytoplasmic labelling was unchanged and nuclear labelling was increased. Small amounts of prosomal proteins p23K and p29K were found on the outer membrane of un-induced cells. While there was no labelling on the outer membrane of RA + VD-induced cells, p23K protein increased on the plasma membrane of PMA-induced cells. The prosome-like particle protein p21K was not present to any significant extent in the intracellular compartment of control or induced cells; however, p21K was detected on the outer surface of control cells and was increased only in PMA-induced cells. The culture medium of control and induced cells contained no p21K, p23K, p29K or p31K. RA + VD seemed to induce a general decrease of prosomal subunits within the cells and at the outer surface, whereas PMA caused a migration toward the plasma membrane and an increase at the outer surface. These changes in the distribution and type of prosomes in RA + VD- and PMA-induced cells indicate that prosomes may play a part in differentiation, especially p23K which is the most highly expressed protein among those studied and presents the more important changes.
蛋白酶体（蛋白酶体/多催化蛋白酶（MCP）复合物）是由28个亚基组成的可变组成的蛋白质颗粒，具有蛋白酶活性。我们研究了U937细胞分化过程中蛋白酶体亚基p29K、p31K和高表达的p23K的变化。对照细胞的细胞质中几乎没有蛋白酶体亚基p31K，而在细胞核和细胞质中均检测到p29K抗原；在细胞质中发现的p23K抗原比在细胞核中多。流式细胞术显示，在佛波酯-肉豆蔻酸-乙酸酯（PMA）和视黄酸加1,25-二羟基胆钙化醇（RA + VD）诱导的分化过程中，蛋白酶体在细胞内呈双相减少。p23K和p29K在分化细胞的细胞质和细胞核中均减少，尽管在PMA诱导的细胞中，p23K抗原集中在囊泡和质膜附近。p31K抗原在RA + VD诱导的细胞中消失，而在PMA诱导的细胞中，细胞质标记未改变，细胞核标记增加。在未诱导细胞的外膜上发现少量蛋白酶体蛋白p23K和p29K。虽然RA + VD诱导的细胞外膜上没有标记，但PMA诱导的细胞的质膜上p23K蛋白增加。在对照细胞或诱导细胞的细胞内区室中，蛋白酶体样颗粒蛋白p21K含量均不显著；然而，在对照细胞的外表面检测到p21K，且仅在PMA诱导的细胞中增加。对照细胞和诱导细胞的培养基中均不含p21K、p23K、p29K或p31K。RA + VD似乎诱导细胞内和细胞外表面的蛋白酶体亚基普遍减少，而PMA则导致其向质膜迁移并在细胞外表面增加。RA + VD和PMA诱导的细胞中蛋白酶体分布和类型的这些变化表明，蛋白酶体可能在分化中起作用，尤其是p23K，它是所研究蛋白质中表达最高的，且呈现出更重要的变化。
