Slow oscillations persist in pancreatic beta cells lacking phosphofructokinase M
Slow oscillations persist in pancreatic beta cells lacking phosphofructokinase M
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缺乏磷酸果糖激酶 M 的胰腺 β 细胞中持续存在缓慢振荡
DOI：
10.1016/j.bpj.2022.01.027
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发表时间：
2022
影响因子：
3.4
通讯作者：
Bertram, Richard
中科院分区：
文献类型：
--
作者：
Marinelli, Isabella;Parekh, Vishal;Fletcher, Patrick;Thompson, Benjamin;Ren, Jinhua;Tang, Xiaoqing;Saunders, Thomas L.;Ha, Joon;Sherman, Arthur;Bertram, Richard
胰腺β细胞的脉冲式胰岛素分泌对于体内严格的葡萄糖控制是必要的。糖酵解振荡被认为是产生胰岛素脉冲分泌电振荡的机制。糖酵解酶6-磷酸果糖激酶-1（PFK）从果糖-6-磷酸合成果糖-1，6-二磷酸（FBP）。已经提出，在胰岛中观察到的缓慢的电振荡和Ca 2+振荡（3-5分钟的周期）是由FBP对PFKM的变构反馈激活引起的。胰腺β细胞表达三种PFK同工酶：PFKL、PFKM和PFKP。先前的一项研究使用基因陷阱策略删除PfKm，使小鼠缺乏PFKM，导致全球PfKm表达的马赛克减少，但从小鼠分离的胰岛仍然表现出缓慢的Ca 2+振荡。然而，这些胰岛仍然表达残余PFKM蛋白。因此，为了更充分地测试β细胞PFKM负责缓慢胰岛振荡的假设，我们制作了完全缺乏PFKM的β细胞特异性敲除小鼠。虽然PFKM缺失导致体内微妙的代谢变化，但从这些小鼠中分离的胰岛继续表现出电活性、β细胞Ca 2+浓度和糖酵解的缓慢振荡，如使用PKAR（一种FBP报告基因/生物传感器）所测量的。此外，用β细胞活性的数学模型获得的模拟表明，尽管PFKM损失，但只要存在其他PFK同种型之一，如PFKP，即使其表达水平不变，缓慢振荡也可以持续。因此，虽然我们认为PFKM可能是野生型胰岛缓慢振荡的主要调节因子，但PFKP可以提供功能冗余。我们的模型还表明，PFKM可能占主导地位，在体内，因为它胜过PFKP与其较高的FBP亲和力和较低的ATP亲和力。因此，我们提出，异构体冗余可能会拯救β细胞的关键生理过程中的某些关键基因的情况下。
Pulsatile insulin secretion by pancreatic beta cells is necessary for tight glucose control in the body. Glycolytic oscillations have been proposed as the mechanism for generating the electrical oscillations underlying pulsatile insulin secretion. The glycolytic enzyme 6-phosphofructokinase-1 (PFK) synthesizes fructose-1,6-bisphosphate (FBP) from fructose-6-phosphate. It has been proposed that the slow electrical and Ca2+oscillations (periods of 3–5 min) observed in islets result from allosteric feedback activation of PFKM by FBP. Pancreatic beta cells express three PFK isozymes: PFKL, PFKM, and PFKP. A prior study of mice that were engineered to lack PFKM using a gene-trap strategy to deletePfkmproduced a mosaic reduction in globalPfkmexpression, but the islets isolated from the mice still exhibited slow Ca2+oscillations. However, these islets still expressed residual PFKM protein. Thus, to more fully test the hypothesis that beta cell PFKM is responsible for slow islet oscillations, we made a beta-cell-specific knockout mouse that completely lacked PFKM. While PFKM deletion resulted in subtle metabolic changesin vivo, islets that were isolated from these mice continued to exhibit slow oscillations in electrical activity, beta cell Ca2+concentrations, and glycolysis, as measured using PKAR, an FBP reporter/biosensor. Furthermore, simulations obtained with a mathematical model of beta cell activity shows that slow oscillations can persist despite PFKM loss provided that one of the other PFK isoforms, such as PFKP, is present, even if its level of expression is unchanged. Thus, while we believe that PFKM may be the main regulator of slow oscillations in wild-type islets, PFKP can provide functional redundancy. Our model also suggests that PFKM likely dominates, in vivo, because it outcompetes PFKP with its higher FBP affinity and lower ATP affinity. We thus propose that isoform redundancy may rescue key physiological processes of the beta cell in the absence of certain critical genes.