大鼠肝脏中环磷酸腺苷依赖性蛋白激酶I和II的含量受饮食的差异调节。

The amounts of rat liver cyclic AMP-dependent protein kinase I and II are differentially regulated by diet.

作者信息

Ekanger R, Vintermyr O K, Døskeland S O

机构信息

Department of Anatomy, University of Bergen, Norway.

出版信息

Biochem J. 1988 Dec 1;256(2):447-52. doi: 10.1042/bj2560447.

DOI:10.1042/bj2560447

PMID:2851990

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1135430/

Abstract

The fluctuations in rat hepatocyte volume and protein content in response to dietary perturbations (starvation, protein restriction, refeeding) were accompanied by corresponding fluctuations in the amount of the regulatory (R) and catalytic (C) subunits of cyclic AMP-dependent protein kinase. Thus the intracellular concentration of this key enzyme was adjusted to be near constant. 2. The adjustment of cellular R was accomplished almost exclusively by regulating cytosolic RI (R subunit of type I kinase). The preferential down-regulation of cytosolic RI in response to starvation/protein restriction indicates that particulate RI and cytosolic as well as particulate RII are more resistant to breakdown during general catabolism in the hepatocyte. 3. The diet-induced fluctuations of kinase subunits were uniformly distributed in all populations of parenchymatous hepatocytes, regardless of their size and density. It is thus possible to isolate hepatocytes with uniformly altered RI/RII ratio from livers of rats with different feeding regimens. 4. The binding of endogenous cyclic AMP to RI and RII was similar in livers with high RI/RII ratio (fed rats) and low RI/RII ratio (fasted rats) as well as in hepatocytes isolated from fasted rats. Under the conditions of the experiment (short-term stimulation by glucagon), therefore, neither the dietary state nor the RI/RII ratio seemed to affect the apparent affinity of the isoreceptors for cyclic AMP. However, RI appeared to show a slightly higher co-operativity of intracellular cyclic AMP binding than did RII in all states.

摘要

大鼠肝细胞体积和蛋白质含量对饮食扰动（饥饿、蛋白质限制、再喂养）的波动，伴随着环磷酸腺苷依赖性蛋白激酶调节（R）亚基和催化（C）亚基数量的相应波动。因此，这种关键酶的细胞内浓度被调节至接近恒定。2. 细胞R的调节几乎完全通过调节胞质RI（I型激酶的R亚基）来完成。饥饿/蛋白质限制时胞质RI的优先下调表明，颗粒性RI以及胞质和颗粒性RII在肝细胞一般分解代谢过程中对降解更具抗性。3. 饮食诱导的激酶亚基波动在所有实质肝细胞群体中均匀分布，无论其大小和密度如何。因此，有可能从不同喂养方案的大鼠肝脏中分离出RI/RII比值均匀改变的肝细胞。4. 在RI/RII比值高的肝脏（喂食大鼠）和RI/RII比值低的肝脏（禁食大鼠）以及从禁食大鼠分离的肝细胞中，内源性环磷酸腺苷与RI和RII的结合相似。因此，在实验条件下（胰高血糖素短期刺激），饮食状态和RI/RII比值似乎都不影响同种受体对环磷酸腺苷的表观亲和力。然而，在所有状态下，RI在细胞内环磷酸腺苷结合方面似乎比RII表现出略高的协同性。