scholarly journals Insights into the residence in lipid rafts of adenylyl cyclase AC8 and its regulation by capacitative calcium entry

2009 ◽  
Vol 296 (3) ◽  
pp. C607-C619 ◽  
Author(s):  
Mario Pagano ◽  
Michael A. Clynes ◽  
Nanako Masada ◽  
Antonio Ciruela ◽  
Laura-Jo Ayling ◽  
...  
Keyword(s):  
Adenylyl Cyclase ◽  
Lipid Rafts ◽  
Leucine Zipper ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Adenylyl Cyclases ◽  
Leucine Zipper Motif ◽  
Capacitative Calcium Entry ◽  
Lipid Raft Microdomains ◽  
Adenylyl Cyclase 8

Adenylyl cyclases (ACs) are a family of critically important signaling molecules that are regulated by multiple pathways. Adenylyl cyclase 8 (AC8) is a Ca2+ stimulated isoform that displays a selective regulation by capacitative Ca2+ entry (CCE), the process whereby the entry of Ca2+ into cells is triggered by the emptying of intracellular stores. This selectivity was believed to be achieved through the localization of AC8 in lipid raft microdomains, along with components of the CCE apparatus. In the present study, we show that an intact leucine zipper motif is required for the efficient N-linked glycosylation of AC8, and that this N-linked glycosylation is important to target AC8 into lipid rafts. Disruption of the leucine zipper by site-directed mutagenesis results in the elimination of N-glycosylated forms and their exclusion from lipid rafts. Mutants of AC8 that cannot be N-glycosylated are not demonstrably associated with rafts, although they can still be regulated by CCE; however, raft integrity is required for the regulation of these mutants. These findings suggest that raft localized proteins in addition to AC8 are needed to mediate its regulation by CCE.

scholarly journals Dimerization mediated through a leucine zipper activates the oncogenic potential of the met receptor tyrosine kinase.

1993 ◽  
Vol 13 (11) ◽  
pp. 6711-6722 ◽  
Author(s):  
G A Rodrigues ◽  
M Park
Keyword(s):  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Leucine Zipper ◽  
Kinase Domain ◽  
Site Directed Mutagenesis ◽  
Leucine Zipper Motif ◽  
Transforming Activity ◽  
Met Oncogene ◽  
Hepatocyte Growth

Oncogenic activation of the met (hepatocyte growth factor/scatter factor) receptor tyrosine kinase involves a genomic rearrangement that generates a hybrid protein containing tpr-encoded sequences at its amino terminus fused directly to the met-encoded receptor kinase domain. Deletion of Tpr sequences abolishes the transforming ability of this protein, implicating this region in oncogenic activation. We demonstrate, by site-directed mutagenesis and coimmunoprecipitation experiments, that a leucine zipper motif within Tpr mediates dimerization of the tpr-met product and is essential for the transforming activity of the met oncogene. By analogy with ligand-stimulated activation of receptor tyrosine kinases, we propose that constitutive dimerization mediated by a leucine zipper motif within Tpr is responsible for oncogenic activation of the Met kinase. The possibility that this mechanism of activation represents a paradigm for a class of receptor tyrosine kinase oncogenes activated by DNA rearrangement is discussed.

Dimerization mediated through a leucine zipper activates the oncogenic potential of the met receptor tyrosine kinase

1993 ◽  
Vol 13 (11) ◽  
pp. 6711-6722
Author(s):  
G A Rodrigues ◽  
M Park
Keyword(s):  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Leucine Zipper ◽  
Kinase Domain ◽  
Site Directed Mutagenesis ◽  
Leucine Zipper Motif ◽  
Transforming Activity ◽  
Met Oncogene ◽  
Hepatocyte Growth

Oncogenic activation of the met (hepatocyte growth factor/scatter factor) receptor tyrosine kinase involves a genomic rearrangement that generates a hybrid protein containing tpr-encoded sequences at its amino terminus fused directly to the met-encoded receptor kinase domain. Deletion of Tpr sequences abolishes the transforming ability of this protein, implicating this region in oncogenic activation. We demonstrate, by site-directed mutagenesis and coimmunoprecipitation experiments, that a leucine zipper motif within Tpr mediates dimerization of the tpr-met product and is essential for the transforming activity of the met oncogene. By analogy with ligand-stimulated activation of receptor tyrosine kinases, we propose that constitutive dimerization mediated by a leucine zipper motif within Tpr is responsible for oncogenic activation of the Met kinase. The possibility that this mechanism of activation represents a paradigm for a class of receptor tyrosine kinase oncogenes activated by DNA rearrangement is discussed.

scholarly journals Analysis of the Essential Cell Division Gene ftsL ofBacillus subtilis by Mutagenesis and Heterologous Complementation

2000 ◽  
Vol 182 (19) ◽  
pp. 5572-5579 ◽  
Author(s):  
Jörg Sievers ◽  
Jeff Errington
Keyword(s):  
Cell Division ◽  
Leucine Zipper ◽  
Stop Codon ◽  
Random Mutagenesis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Induced Mutations ◽  
Phenotypic Effect

ABSTRACT The ftsL gene is required for the initiation of cell division in a broad range of bacteria. Bacillus subtilis ftsL encodes a 13-kDa protein with a membrane-spanning domain near its N terminus. The external C-terminal domain has features of an α-helical leucine zipper, which is likely to be involved in the heterodimerization with another division protein, DivIC. To determine what residues are important for FtsL function, we used both random and site-directed mutagenesis. Unexpectedly, all chemically induced mutations fell into two clear classes, those either weakening the ribosome-binding site or producing a stop codon. It appears that the random mutagenesis was efficient, so many missense mutations must have been generated but with no phenotypic effect. Substitutions affecting hydrophobic residues in the putative coiled-coil domain, introduced by site-directed mutagenesis, also gave no observable phenotype except for insertion of a helix-breaking proline residue, which destroyed FtsL function. ftsL homologues cloned from three diverseBacillus species, Bacillus licheniformis,Bacillus badius, and Bacillus circulans, could complement an ftsL null mutation in B. subtilis, even though up to 66% of the amino acid residues of the predicted proteins were different from B. subtilisFtsL. However, the ftsL gene from Staphylococcus aureus (whose product has 73% of its amino acids different from those of the B. subtilis ftsL product) was not functional. We conclude that FtsL is a highly malleable protein that can accommodate a large number of sequence changes without loss of function.

The site-directed mutagenesis and prokaryotic expression of midkine gene in Cynoglossus semilaevis

2013 ◽  
Vol 37 (3) ◽  
pp. 330
Author(s):  
Yanan WANG ◽  
Xudong LIU ◽  
Linlin MU ◽  
Zhipeng LIU ◽  
Chunmei LI ◽  
...  
Keyword(s):  
Prokaryotic Expression ◽  
Cynoglossus Semilaevis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis
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