Isseroff R R, Stephens L E, Gross J L
Department of Dermatology, School of Medicine, University of California, Davis 95616.
J Cell Physiol. 1989 Nov;141(2):235-42. doi: 10.1002/jcp.1041410202.
The activation of protein kinase C (PKC) by diacylglycerol or tumor promoters plays a pivotal role in signal transduction and subsequent activation of cellular processes. Since the activity of this enzyme is dependent on its immediate lipid domain, its relative distribution within the cell may be an important regulatory mechanism. We report here a relative decrease in PKC/phorbol ester receptor associated with the particulate fraction of mouse keratinocytes induced to differentiate by two separate systems. First, proliferating keratinocytes maintained in low Ca2+ (0.09 mM) serum-free medium were induced to differentiate rapidly by the addition of Ca2+ (1.8 mM). A 1.4-fold decrease in the percent of total phorbol receptor binding activity present in the particulate fraction and concomitant increase in binding in the cytosol fraction was evident 20 min after the Ca2+ addition. Second, in keratinocytes that differentiate over a 6 day cultivation period in serum-containing medium with Ca2+ concentration of 1.8 mM, a significant decrease in the percent of the phorbol receptor binding activity present in the particulate fraction was observed as the culture begins to differentiate on days 3 and 4. Maximal phorbol ester binding in the particulate fraction corresponded to the proliferative phase of the culture (day 2), while lower levels of PKC/phorbol ester binding to particulate fractions were noted during the early differentiative phase (days 3 and 4). Addition of the synthetic diacylglycerols 1-oleoyl-2-acetylglycerol or L-alpha-1,2 dioctanyl glycerol at 30 micrograms/ml to proliferating keratinocyte cultures induced a modest increase in two markers of terminal differentiation: cornified envelope formation and transglutaminase levels. These findings, taken together, support the hypothesis that PKC activation plays a role in the initial signalling events for keratinocyte differentiation.
二酰基甘油或肿瘤启动子对蛋白激酶C（PKC）的激活在信号转导及随后的细胞过程激活中起关键作用。由于该酶的活性依赖于其紧邻的脂质结构域，其在细胞内的相对分布可能是一种重要的调节机制。我们在此报告，在由两种不同系统诱导分化的小鼠角质形成细胞的微粒部分中，PKC/佛波酯受体相对减少。首先，在低钙（0.09 mM）无血清培养基中培养的增殖角质形成细胞，通过添加钙（1.8 mM）可迅速诱导分化。添加钙20分钟后，微粒部分中总佛波酯受体结合活性的百分比明显下降1.4倍，同时胞质部分的结合增加。其次，在含1.8 mM钙的培养基中培养6天的角质形成细胞中，随着培养在第3天和第4天开始分化，微粒部分中佛波酯受体结合活性的百分比显著下降。微粒部分中最大的佛波酯结合对应于培养的增殖期（第2天），而在早期分化期（第3天和第4天），微粒部分中PKC/佛波酯的结合水平较低。向增殖的角质形成细胞培养物中添加30微克/毫升的合成二酰基甘油1-油酰基-2-乙酰甘油或L-α-1,2-二辛酰甘油，可使终末分化的两个标志物：角质包膜形成和转谷氨酰胺酶水平适度增加。综上所述，这些发现支持了PKC激活在角质形成细胞分化的初始信号事件中起作用这一假说。
