Multiplicity in type V adenylylcyclase: type V-a and type V-b

Iwami, Gensho; Akanuma, Masahiko; Kawabe, Jun‐ichi; Cannon, Paul J.; Homcy, Charles J.; Ishikawa, Yoshihiro

doi:10.1016/0303-7207(95)03514-8

Cited by 14 publications

(5 citation statements)

References 10 publications

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“…A third isoform is missing a region, which seems to be important for calcium/calmodulin regulation. Alternatively spliced forms of tmAC III in mammalian germ cells, 79 tmAC IV in uterine myometrium, 80 and of tmAC V and VI have been identified, [81][82][83] but their biochemical properties or physiological significance have not yet been elucidated.…”

Section: Isoform Diversitymentioning

confidence: 99%

Molecular Details of cAMP Generation in Mammalian Cells: A Tale of Two Systems

Kamenetsky

Middelhaufe

Bank

et al. 2006

Journal of Molecular Biology

293

340

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The second messenger cAMP has been extensively studied for half a century, but the plethora of regulatory mechanisms controlling cAMP synthesis in mammalian cells is just beginning to be revealed. In mammalian cells, cAMP is produced by two evolutionary related families of adenylyl cyclases, soluble adenylyl cyclases (sAC) and transmembrane adenylyl cyclases (tmAC). These two enzyme families serve distinct physiological functions. They share a conserved overall architecture in their catalytic domains and a common catalytic mechanism, but they differ in their sub-cellular localizations and responses to various regulators. The major regulators of tmACs are heterotrimeric G proteins, which transduce extracellular signals via G protein-coupled receptors. sAC enzymes, in contrast, are regulated by the intracellular signaling molecules bicarbonate and calcium. Here, we discuss and compare the biochemical, structural and regulatory characteristics of the two mammalian AC families. This comparison reveals the mechanisms underlying their different properties but also illustrates many unifying themes for these evolutionary related signaling enzymes.

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Section: Isoform Diversitymentioning

confidence: 99%

Molecular Details of cAMP Generation in Mammalian Cells: A Tale of Two Systems

Kamenetsky

Middelhaufe

Bank

et al. 2006

Journal of Molecular Biology

293

340

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“…The major difference between canine and human AC V and between human AC V and human AC VI lies in the N terminus. Human, rat, and rabbit AC V share similar N termini; however, canine share almost no homology in this region due to differential splicing (34). The N terminus of human AC V also shares almost no homology with that of AC VI.…”

Section: Modeling Of G␣ S and G␣ I Regulation Of Ac Vi-our Model For mentioning

confidence: 99%

Modeling of Gαs and Gαi Regulation of Human Type V and VI Adenylyl Cyclase

Chen-Goodspeed

Lukan

Dessauer

2005

Journal of Biological Chemistry

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We examined the kinetics of G␣ s and G␣ i regulation of human type V and type VI adenylyl cyclase (AC V and AC VI) in order to better model interactions between AC and its regulators. Activation of AC VI by G␣ s displayed classical Michaelis-Menten kinetics, whereas AC V activation by G␣ s was cooperative with a Hill coefficient of 1.4. The basal activity of human AC V, but not that of AC VI, was inhibited by G␣ i . Both enzymes showed greater inhibition by G␣ i at low G␣ s concentrations; however, human AC V was activated by G␣ i at high G␣ s concentrations. Neither regulator had an effect on the K m for Mg-ATP. Mutations made within the G␣ s binding pocket of AC V (N1090D) and VI (F1078S) displayed 6-and 14-fold greater EC 50 values for G␣ s activation but had no effect on G␣ i inhibition of basal activity or K m for Mg-ATP. G␣ s -stimulated AC VI-F1078S was not significantly inhibited by G␣ i , despite normal inhibition by G␣ i upon forskolin stimulation. Mechanistic models for G␣ s and G␣ i regulation of AC V and VI were derived to describe these results. Our models are consistent with previous studies, predicting a decrease in affinity of G␣ i in the presence of G␣ s . For AC VI, G␣ s is required for inhibition but not binding by G␣ i . For AC V, binding of two molecules of G␣ s and G␣ i to an AC dimer are required to fully describe the data. These models highlight the differences between AC V and VI and the complex interactions with two important regulators.The key to regulation of adenylyl cyclase (AC) 1 activity is the conformational state of the enzyme at the interface of the two large cytoplasmic domains (1-3). G␣ s binds to the second cytoplasmic (C 2 ) domain of AC and increases the affinity of the two domains for one another to promote catalysis (4 -8). G␣ i works in direct opposition to G␣ s , binding to the first cytoplasmic domain (C 1 ) and decreasing domain interaction to reduce formation of the AC catalytic site (3, 9).Although conformational changes at the domain interface are critical for regulation, other regions of AC play important roles as well. For example, the N terminus of rat AC VI interacts with the C 1 domain to modulate G␣ i -mediated inhibition (10) and glycosylation of AC VI may alter regulatory properties of the enzyme (11). Although native and recombinant G␣ s have similar effects on the cytoplasmic domains of AC, activation of full-length AC is less effectively inhibited by G␣ i upon stimulation of native versus recombinant G␣ s (12). Kleuss and Krause speculate that the palmitate on native G␣ s competes with the myristate on G␣ i for a hydrophobic binding pocket on AC (12). Previous studies by Taussig et al. (13) suggest that both G␣ s and G␣ i are bound simultaneously to the enzyme, seemingly in contradiction to studies using the independently expressed cytoplasmic domains (3). In an attempt to fully understand the regulation of full-length human AC V and VI, we have modeled the kinetics of G␣ s /G␣ i regulation.Types V and VI AC are generally grouped together as being hig...

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“…PCR amplification and sequencing of the region of ADCY6 containing exon 13, intron 14 and exon 14 verify these results. Other experimental evidence for splice variants of human adenylyl cyclases have not previously been reported; however, three alternatively spliced rat AC8 messages have been identified with altered structural and enzymatic properties (13) and two splice variants of AC 5 have been reported in dog and rat (14,15).…”

Section: Determining the Gene Organization Of Adcy6mentioning

confidence: 95%