Activation of adenylyl cyclase in Chlamydomonas reinhardtii by adhesion and by heat.
Activation of adenylyl cyclase in Chlamydomonas reinhardtii by adhesion and by heat.
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通过粘附和加热激活莱茵衣藻中的腺苷酸环化酶。
DOI：
10.1083/jcb.122.1.137
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Goodenough,UW
中科院分区：
文献类型：
--
作者：
Saito,T;Small,L;Goodenough,UW
莱茵衣原体配子之间的粘附导致cAMP水平迅速升高，从而刺激交配反应和合子细胞融合（Pasquale和Goodenough，1987）。我们在这里表明，性粘附在体内的结果在鞭毛腺苷酸环化酶活性的双重刺激时，酶随后在体外测定，刺激，这是专门阻止镉2+。通过可溶性交联试剂（抗血清和伴刀豆球蛋白A）的体外呈递也可引起双重刺激。相比之下，Zhang等人（1991）首次描述的体外暴露于40 ℃对鞭毛环化酶的10-30倍刺激对Cd 2+不敏感，但对三氟哌嗪和地布卡因等药物敏感。营养酶和配子酶显示出双重刺激的能力，但当配子融合形成合子时失去了这种能力;相反，配子酶和合子酶显示出10倍刺激，但营养酶没有。信号缺陷突变体imp-3不能产生正常的交配触发的cAMP产生，并且可以被外源性二丁酰cAMP拯救。它显示出正常的鞭毛环化酶活性基础率以及性粘附和可溶性交联剂的正常两倍刺激，但在40摄氏度的激活中存在缺陷。配子体细胞腺苷酸环化酶的刺激时，野生型鞭毛，而不是IMP-3鞭毛，在体内进行粘附相互作用，它可以直接刺激在体外的cAMP介绍。我们建议，鞭毛环化酶刺激的两个水平反映了一个单一的环化酶的激活，与IMP-3在第二步中被阻止，或者两个不同的鞭毛酶的顺序激活，与IMP-3缺陷的第二个酶的顺序步骤。我们进一步提出，细胞体酶被激活的cAMP时，鞭毛环化酶活性被充分刺激产生的。
Adhesion between Chlamydomonas reinhardtii gametes generates a rapid rise in cAMP levels which stimulates mating responses and zygotic cell fusion (Pasquale and Goodenough, 1987). We show here that sexual adhesion in vivo results in a twofold stimulation of flagellar adenylyl cyclase activity when the enzyme is subsequently assayed in vitro, a stimulation that is specifically blocked by Cd2+. A twofold stimulation is also elicited by the in vitro presentation of soluble cross-linking reagents (antisera and concanavalin A). In contrast, the 10-30-fold stimulation of the flagellar cyclase by in vitro exposure to 40 degrees C, first described by Zhang et al. (1991), is insensitive to Cd2+ but sensitive to such drugs as trifluoperizine and dibucaine. The capacity for twofold stimulation is displayed by the vegetative and gametic enzymes but is lost when gametes fuse to form zygotes; in contrast, the 10-fold stimulation is displayed by the gametic and zygotic enzymes but not the vegetative enzyme. The signal-defective mutant imp-3 fails to generate the normal mating-triggered cAMP production and can be rescued by exogenous dibutyryl cAMP. It displays normal basal rates of flagellar cyclase activity and a normal twofold stimulation by sexual adhesion and by soluble cross-linkers, but it is defective in 40 degrees C activation. The gametic cell-body adenylyl cyclase is stimulated when wild-type flagella, but not imp-3 flagella, undergo adhesive interactions in vivo, and it can be directly stimulated in vitro by cAMP presentation. We propose that the two levels of flagellar cyclase stimulation reflect either sequential steps in the activation of a single cyclase enzyme, with imp-3 blocked in the second step, or else the sequential activation of two different flagellar enzymes, with imp-3 defective in the second enzyme. We further propose that the cell-body enzyme is activated by the cAMP that is generated when flagellar cyclase activity is fully stimulated.