OR01-04 Kruppel-Like Factors 9 and 13 Cooperate to Maintain Mammalian Neuronal Differentiation

Abstract During development of the central nervous system, neural cells respond to several external cues that influence cell proliferation, differentiation, axonal growth and synaptogenesis. Thyroid hormone plays a critical role in each of these processes. Previously, we showed that Krüppel-like factor 9 (KLF9), a zinc finger transcription factor, is strongly and directly induced by liganded thyroid hormone receptors, and it mediates the actions of thyroid hormone on neuronal differentiation during late fetal development. Here we analyzed the molecular mechanisms by which KLF9 maintains neuronal structure, and inhibits regeneration in juvenile and adult neuronal cells. We also investigated the actions of the closely related transcription factor KLF13, which is paralogous to KLF9. We engineered the adult mouse hippocampus-derived cell line HT22 to control Klf9 or Klf13 expression by addition of doxycycline. We also used CRISPR/Cas9 genome editing to generate Klf9 or Klf13 knock out (KO), and Klf9+Klf13 double KO HT22 cell lines. To induce neurite outgrowth, we treated cells with forskolin (FK)+IBMX, which increases intracellular cAMP; elevated cAMP is a hallmark of regenerative responses of neurons to injury. Our results show that FK+IBMX increased neurite length in the parent HT22 cell line, and this action was enhanced in Klf9 and Klf13 single KO cells, and was even greater in double KO cells. By contrast, the stimulatory effect of FK+IBMX on neurite outgrowth was blocked by simultaneous forced expression of Klf9 or Klf13 in parent HT22 cells. This effect on neurite outgrowth was confirmed in primary mouse hippocampal neurons, where electroporation of expression plasmids for Klf9 or Klf13 suppressed FK+IBMX-induced neurite extension compared with empty vector-transfected cells. Analysis of RNA-seq data obtained from HT22 cells following 8 hr of induced Klf9 or Klf13 expression showed that both proteins impact the cAMP signaling pathway. Using transfection-reporter assays and chromatin immunoprecipitation, we confirmed that several genes in this pathway are direct targets of both KLFs. Our findings suggest that KLF9 and KLF13 may cooperate to maintain the differentiated state of mammalian neurons and thereby block regeneration, in part, by repressing the cAMP signaling pathway.

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Sesamin induces melanogenesis by microphthalmia-associated transcription factor and tyrosinase up-regulation via cAMP signaling pathway

Acta Biochimica et Biophysica Sinica ◽

10.1093/abbs/gmr078 ◽

2011 ◽

Vol 43 (10) ◽

pp. 763-770 ◽

Cited By ~ 13

Author(s):

Z. Jiang ◽

S. Li ◽

Y. Liu ◽

P. Deng ◽

J. Huang ◽

...

Keyword(s):

Transcription Factor ◽

Signaling Pathway ◽

Camp Signaling ◽

Camp Signaling Pathway

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cAMP-signaling pathway acts in selective synergism with glucose or tolbutamide to increase cytosolic Ca2+ in rat pancreatic beta-cells

Diabetes ◽

10.2337/diabetes.45.3.295 ◽

1996 ◽

Vol 45 (3) ◽

pp. 295-301 ◽

Cited By ~ 8

Author(s):

K. Yaekura ◽

M. Kakei ◽

T. Yada

Keyword(s):

Signaling Pathway ◽

Beta Cells ◽

Pancreatic Beta Cells ◽

Camp Signaling ◽

Camp Signaling Pathway

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Role of cAMP in Double Switch of Glucagon Secretion

Cells ◽

10.3390/cells10040896 ◽

2021 ◽

Vol 10 (4) ◽

pp. 896

Author(s):

Jan Zmazek ◽

Vladimir Grubelnik ◽

Rene Markovič ◽

Marko Marhl

Keyword(s):

Glucose Metabolism ◽

Signaling Pathway ◽

Cell Model ◽

Dominant Role ◽

Glucagon Secretion ◽

Camp Signaling ◽

Independent Manner ◽

Metabolic Switch ◽

Camp Signaling Pathway ◽

Double Switch

Glucose metabolism plays a crucial role in modulating glucagon secretion in pancreatic alpha cells. However, the downstream effects of glucose metabolism and the activated signaling pathways influencing glucagon granule exocytosis are still obscure. We developed a computational alpha cell model, implementing metabolic pathways of glucose and free fatty acids (FFA) catabolism and an intrinsically activated cAMP signaling pathway. According to the model predictions, increased catabolic activity is able to suppress the cAMP signaling pathway, reducing exocytosis in a Ca2+-dependent and Ca2+ independent manner. The effect is synergistic to the pathway involving ATP-dependent closure of KATP channels and consequent reduction of Ca2+. We analyze the contribution of each pathway to glucagon secretion and show that both play decisive roles, providing a kind of “secure double switch”. The cAMP-driven signaling switch plays a dominant role, while the ATP-driven metabolic switch is less favored. The ratio is approximately 60:40, according to the most recent experimental evidence.

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Assessment of cellular mechanisms contributing to cAMP compartmentalization in pulmonary microvascular endothelial cells

AJP Cell Physiology ◽

10.1152/ajpcell.00361.2011 ◽

2012 ◽

Vol 302 (6) ◽

pp. C839-C852 ◽

Cited By ~ 38

Author(s):

Wei P. Feinstein ◽

Bing Zhu ◽

Silas J. Leavesley ◽

Sarah L. Sayner ◽

Thomas C. Rich

Keyword(s):

Endothelial Cells ◽

Adenylyl Cyclase ◽

Signaling Pathway ◽

Camp Signaling ◽

Microvascular Endothelial Cells ◽

Camp Production ◽

Barrier Integrity ◽

Pulmonary Microvascular Endothelial Cells ◽

Camp Signaling Pathway ◽

Microvascular Endothelial

Cyclic AMP signals encode information required to differentially regulate a wide variety of cellular responses; yet it is not well understood how information is encrypted within these signals. An emerging concept is that compartmentalization underlies specificity within the cAMP signaling pathway. This concept is based on a series of observations indicating that cAMP levels are distinct in different regions of the cell. One such observation is that cAMP production at the plasma membrane increases pulmonary microvascular endothelial barrier integrity, whereas cAMP production in the cytosol disrupts barrier integrity. To better understand how cAMP signals might be compartmentalized, we have developed mathematical models in which cellular geometry as well as total adenylyl cyclase and phosphodiesterase activities were constrained to approximate values measured in pulmonary microvascular endothelial cells. These simulations suggest that the subcellular localizations of adenylyl cyclase and phosphodiesterase activities are by themselves insufficient to generate physiologically relevant cAMP gradients. Thus, the assembly of adenylyl cyclase, phosphodiesterase, and protein kinase A onto protein scaffolds is by itself unlikely to ensure signal specificity. Rather, our simulations suggest that reductions in the effective cAMP diffusion coefficient may facilitate the formation of substantial cAMP gradients. We conclude that reductions in the effective rate of cAMP diffusion due to buffers, structural impediments, and local changes in viscosity greatly facilitate the ability of signaling complexes to impart specificity within the cAMP signaling pathway.

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