scholarly journals Mapping of the functional determinants of the integrin beta 1 cytoplasmic domain by site-directed mutagenesis.

1990 ◽  
Vol 1 (8) ◽  
pp. 597-604 ◽  
Author(s):  
E E Marcantonio ◽  
J L Guan ◽  
J E Trevithick ◽  
R O Hynes
Keyword(s):  
Consensus Sequence ◽  
Cytoplasmic Domain ◽  
Site Directed Mutagenesis ◽  
Focal Contact ◽  
Wild Type ◽  
3T3 Cells ◽  
Transmembrane Region ◽  
High Level Expression ◽  
Focal Contacts ◽  
High Level

We describe here the expression of deletion mutants of the cytoplasmic domain of the avian integrin beta 1 subunit. These mutants, which contain termination codons at positions 767, 776, 791, and 800, were transfected into mouse 3T3 cells to determine which sequences were essential for localization of integrins into focal contact sites. In all cases, high-level expression of the truncated avian integrins was obtained. Heterodimers were formed between the exogenous truncated avian beta 1 subunits and endogenous mouse alpha subunits, and these heterodimers were efficiently exported to the cell surface. The longest truncated beta 1 subunit tested, which is only four amino acids shorter than the wild type, does localize to focal contacts. In contrast, beta 1 subunits with moderately long truncations of the cytoplasmic domain failed to localize to focal contacts, including one which contains the consensus sequence for tyrosine phosphorylation. Surprisingly, a mutant subunit in which the bulk of the cytoplasmic domain was missing (but the segment nearest the membrane including the dibasic residues (RR) remained) did localize weakly to focal contacts. These results implicate the peptide segment nearest to the transmembrane region in focal contact localization. In addition, mutant subunits that included this segment together with a larger portion of the cytoplasmic domain did not localize as well as the shorter form, suggesting that these cytoplasmic domain segments are defective, presumably because of abnormal folding.

scholarly journals Expression and function of chicken integrin beta 1 subunit and its cytoplasmic domain mutants in mouse NIH 3T3 cells.

1990 ◽  
Vol 110 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Y Hayashi ◽  
B Haimovich ◽  
A Reszka ◽  
D Boettiger ◽  
A Horwitz
Keyword(s):  
Cell Surface ◽  
Cytoplasmic Domain ◽  
Alpha Subunit ◽  
Immunofluorescent Staining ◽  
Wild Type ◽  
3T3 Cells ◽  
Chimeric Receptors ◽  
Focal Contacts ◽  
Nih 3T3 ◽  
Nih 3T3 Cells

Chicken integrin beta 1 cDNA and its site-directed mutants were cloned into a mammalian expression vector and introduced into mouse NIH 3T3 cells. Stable transfectants expressing the chicken beta 1 subunit or its site-directed mutants were identified by immunostaining with antibodies specific for the chicken integrin beta 1 subunit. The chicken beta 1 proteins were expressed predominately in the endoplasmic reticulum of transfectants and to a lesser degree in the plasma membrane. Immunoblots and immunoprecipitations, using anti-chicken integrin antibodies, revealed three different sizes of the chicken subunit (90, 95, and 120 kD) and a mouse 140-kD alpha subunit. Immunoprecipitations of the cell surface receptors showed only two peptides, an 120-kD beta 1 and an 140-kD alpha subunit. Antibodies perturbing mouse and chicken integrin-specific cell adhesions were used to demonstrate that the chimeric receptors functioned in adhesion to both laminin and fibronectin. Immunofluorescent staining with antibodies specific for either the chicken or mouse receptors showed that both the wild type and the chimeric receptors localized in focal contacts. Several mutations in the cytoplasmic domain were synthesized and used in the transfection experiments. In one mutant the tyrosine (Tyr 788) in the consensus sequence for phosphorylation was replaced by a phenylalanine. In another the lysine (Lys 757) at the end of the membrane spanning region was replaced by a leucine. Both of these mutants formed dimers with mouse alpha subunits, participated in adhesion, localized in focal contacts, and displayed biological properties indistinguishable from the wild-type transfection. In contrast, mutants containing deletions greater than 5-15 amino acids nearest the carboxyl end in the cytoplasmic domain neither promoted adhesion nor localized in focal contacts. They did, however, form heterodimers that were expressed on the cell surface.

Characterization of cDNA encoding mouse DNA repair protein O6-methylguanine-DNA methyltransferase and high-level expression of the wild-type and mutant proteins in E. coli

Biochemistry ◽  
1992 ◽  
Vol 31 (7) ◽  
pp. 1897-1903 ◽  
Author(s):  
Susumu Shiota ◽  
Mathew A. Von Wronski ◽  
Keizo Tano ◽  
Darell D. Bigner ◽  
Thomas P. Brent ◽  
...  
Keyword(s):  
Dna Methyltransferase ◽  
Wild Type ◽  
High Level Expression ◽  
Mutant Proteins ◽  
E Coli ◽  
Methylguanine Dna Methyltransferase ◽  
Repair Protein ◽  
Dna Repair Protein ◽  
High Level

R to Q Amino Acid Substitution in the GFFKR Sequence of the Cytoplasmic Domain of the Integrin IIb Subunit in a Patient With a Glanzmann’s Thrombasthenia-Like Syndrome

Blood ◽  
1998 ◽  
Vol 92 (11) ◽  
pp. 4178-4187 ◽  
Author(s):  
O. Peyruchaud ◽  
A.T. Nurden ◽  
S. Milet ◽  
L. Macchi ◽  
A. Pannochia ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Chinese Hamster ◽  
Cytoplasmic Domain ◽  
Site Directed Mutagenesis ◽  
Heterozygous Mutation ◽  
Polymorphism Analysis ◽  
Wild Type ◽  
Glanzmann’S Thrombasthenia ◽  
Glanzmann's Thrombasthenia

Abstract The integrin IIbβ3 mediates platelet aggregation through its fibrinogen and adhesive protein-binding properties. Particular interest concerns the role of the cytoplasmic domains of IIb and β3. We now report the molecular analysis of IIbβ3 from a patient with a Glanzmann’s thrombasthenia-like syndrome for whom the principal characteristics are an approximate 50% total platelet content of IIbβ3 but with a much lower proportion in the surface pool (Hardisty et al, Blood 80:696, 1992). Polymerase chain reaction (PCR) single-strand conformational polymorphism and DNA sequencing showed a heterozygous mutation giving rise to amino acid substitution R995 to Q in the GFFKR sequence of the cytoplasmic domain of IIb. Reverse transcriptase-PCR and polymorphism analysis only detected mRNA for the mutated allele of the IIb gene and a single allele of the β3 gene in his platelets, suggesting other unidentified defects. Site-directed mutagenesis followed by transient expression of the mutated IIb together with wild-type β3 in Cos-7 cells resulted in a markedly decreased expression of the complex at the cell surface when compared with cells transfected with wild-type IIb and β3. Flow cytometry with PAC-1 and a stable Chinese hamster ovary–transfected cell line showed that the mutated receptor was not locked into a high activation state, although it became so in the presence of the activating antibody, anti-LIBS6. This is the first reported natural mutation in the highly conserved GFFKR sequence of the IIb cytoplasmic domain.

scholarly journals Modulation of β1A Integrin Functions by Tyrosine Residues in the β1 Cytoplasmic Domain

1998 ◽  
Vol 141 (2) ◽  
pp. 527-538 ◽  
Author(s):  
Takao Sakai ◽  
Qinghong Zhang ◽  
Reinhard Fässler ◽  
Deane F. Mosher
Keyword(s):  
Stem Cells ◽  
Cell Adhesion ◽  
Point Mutations ◽  
Cytoplasmic Domain ◽  
Wild Type ◽  
Directed Migration ◽  
Tyrosine Residues ◽  
Impaired Ability ◽  
Focal Contacts ◽  
Activating Mutation

β1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from β1-null stem cells. β1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active α5β1 and α6β1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive β1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type β1A or β1A with the D759A activating mutation of a conserved membrane–proximal aspartate, Y783,795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing β1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type β1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility.

scholarly journals Identification of a UPC2 Homolog inSaccharomyces cerevisiae and Its Involvement in Aerobic Sterol Uptake

2001 ◽  
Vol 183 (3) ◽  
pp. 830-834 ◽  
Author(s):  
Kevin V. Shianna ◽  
W. David Dotson ◽  
Shirley Tove ◽  
Leo W. Parks
Keyword(s):  
Point Mutation ◽  
Wild Type Strain ◽  
Point Mutations ◽  
Transcriptional Activator ◽  
Site Directed Mutagenesis ◽  
Wild Type ◽  
Reading Frame ◽  
Sterol Uptake ◽  
Major Sterol ◽  
High Level

ABSTRACT Saccharomyces cerevisiae normally will not take up sterols from the environment under aerobic conditions. A specific mutant, upc2-1, of the predicted transcriptional activator UPC2 (YDR213w) has been recognized as a strain that allows a high level of aerobic sterol uptake. Another predicted transcriptional activator, the YLR228c gene product, is highly homologous to Upc2p. In fact, at the carboxy terminus 130 of the last 139 amino acids are similar between the two proteins. Since these proteins are very similar, the effect of mutations in the YLR228c open reading frame (ORF) was compared with like alterations in UPC2. First, the YLR228c ORF was insertionally inactivated and crossed with various UPC2constructs. Deletion of YLR228c and UPC2 in combination resulted in nonviability, suggesting that the two proteins have some essential overlapping function. The upc2-1point mutation responsible for aerobic sterol uptake was duplicated in the homologous carboxy region of the YLR228c ORF using site-directed mutagenesis. This mutation on a high-copy vector resulted in an increase in sterol uptake compared to an isogenic wild-type strain. The combination of both point mutations resulted in the greatest level of aerobic sterol uptake. When the YLR228c point mutation was expressed from a low-copy vector there was little if any effect on sterol uptake. Gas chromatographic analysis of the nonsaponifiable fractions of the various strains showed that the major sterol for all YLR228c andUPC2 combinations was ergosterol, the consensus yeast sterol.

R to Q Amino Acid Substitution in the GFFKR Sequence of the Cytoplasmic Domain of the Integrin IIb Subunit in a Patient With a Glanzmann’s Thrombasthenia-Like Syndrome

Blood ◽  
1998 ◽  
Vol 92 (11) ◽  
pp. 4178-4187 ◽  
Author(s):  
O. Peyruchaud ◽  
A.T. Nurden ◽  
S. Milet ◽  
L. Macchi ◽  
A. Pannochia ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Chinese Hamster ◽  
Cytoplasmic Domain ◽  
Site Directed Mutagenesis ◽  
Heterozygous Mutation ◽  
Polymorphism Analysis ◽  
Wild Type ◽  
Glanzmann’S Thrombasthenia ◽  
Glanzmann's Thrombasthenia

The integrin IIbβ3 mediates platelet aggregation through its fibrinogen and adhesive protein-binding properties. Particular interest concerns the role of the cytoplasmic domains of IIb and β3. We now report the molecular analysis of IIbβ3 from a patient with a Glanzmann’s thrombasthenia-like syndrome for whom the principal characteristics are an approximate 50% total platelet content of IIbβ3 but with a much lower proportion in the surface pool (Hardisty et al, Blood 80:696, 1992). Polymerase chain reaction (PCR) single-strand conformational polymorphism and DNA sequencing showed a heterozygous mutation giving rise to amino acid substitution R995 to Q in the GFFKR sequence of the cytoplasmic domain of IIb. Reverse transcriptase-PCR and polymorphism analysis only detected mRNA for the mutated allele of the IIb gene and a single allele of the β3 gene in his platelets, suggesting other unidentified defects. Site-directed mutagenesis followed by transient expression of the mutated IIb together with wild-type β3 in Cos-7 cells resulted in a markedly decreased expression of the complex at the cell surface when compared with cells transfected with wild-type IIb and β3. Flow cytometry with PAC-1 and a stable Chinese hamster ovary–transfected cell line showed that the mutated receptor was not locked into a high activation state, although it became so in the presence of the activating antibody, anti-LIBS6. This is the first reported natural mutation in the highly conserved GFFKR sequence of the IIb cytoplasmic domain.

scholarly journals Ligand-dependent and -independent integrin focal contact localization: the role of the alpha chain cytoplasmic domain.

1993 ◽  
Vol 4 (6) ◽  
pp. 593-604 ◽  
Author(s):  
R Briesewitz ◽  
A Kern ◽  
E E Marcantonio
Keyword(s):  
Cell Lines ◽  
Cellular Localization ◽  
Surface Expression ◽  
Cytoplasmic Domain ◽  
Striking Difference ◽  
Focal Contact ◽  
Integrin Receptors ◽  
Independent Manner ◽  
Contact Sites ◽  
Focal Contacts

Many integrin receptors localize to focal contact sites upon binding their ligand. However, unoccupied integrin receptors do not localize to focal contact sites. Because the integrin beta 1 cytoplasmic domain appears to have a focal contact localization signal, there must be a mechanism by which this domain is kept inactive in the unoccupied state and becomes exposed or activated in the occupied receptor. We considered that this mechanism involves the alpha subunit cytoplasmic domain. To test this hypothesis, we have established two NIH 3T3 cell lines that express either the human alpha 1 wild-type subunit (HA1 cells) or the cytoplasmic domain deleted alpha 1 subunit (CYT cells). Both cell lines express similar levels of the human alpha 1 subunit, and there is no significant effect of the deletion on the dimerization and surface expression of the receptor. Furthermore, the deletion had no effect on the binding or adhesion via alpha 1 beta 1 to its ligand collagen IV. However, when these two cell lines are plated on fibronectin (FN), which is a ligand for alpha 5 beta 1 but not for alpha 1 beta 1, there is a striking difference in the cellular localization of alpha 1 beta 1. The HA1 cells show only alpha 5 in focal contacts, without alpha 1, demonstrating that all of the integrin localization is ligand dependent. In contrast, when the CYT cells are plated on FN, the mutant alpha 1 appears in focal contacts along with the alpha 5/beta 1. Thus, there is both ligand-dependent (alpha 5/beta 1) and ligand-independent (alpha 1/beta 1) focal contact localization in these cells. The truncated alpha 1 also localized to focal contacts in a ligand-independent manner on vitronectin. We conclude that the mutant alpha 1 no longer requires ligand occupancy for focal contact localization. These data strongly suggest that the alpha cytoplasmic domain plays a role in the normal ligand-dependent integrin focal contact localization.

Differential effects of carboxy-terminal sequence deletions on platelet-derived growth factor receptor signaling activities and interactions with cellular substrates

1992 ◽  
Vol 12 (10) ◽  
pp. 4347-4356
Author(s):  
K Seedorf ◽  
B Millauer ◽  
G Kostka ◽  
J Schlessinger ◽  
A Ullrich
Keyword(s):  
Growth Factor ◽  
Phospholipase C ◽  
Growth Factor Receptor ◽  
Cytoplasmic Domain ◽  
Wild Type ◽  
3T3 Cells ◽  
Substrate Phosphorylation ◽  
Phospholipase C Gamma ◽  
Carboxy Terminal ◽  
Nih 3T3

Chimeric receptors composed of the human epidermal growth factor receptor (EGF-R) extracellular domain fused to wild-type and truncated platelet-derived growth factor receptor (PDGF-R) intracellular sequences were stably expressed in NIH 3T3 cells devoid of endogenous EGF-Rs. This experimental system allowed us to investigate the biological activity of PDGF-R cytoplasmic-domain mutants in PDGF-R-responsive NIH 3T3 cells by activating PDGF-specific signaling pathways with EGF. Deletion of 74 carboxy-terminal amino acids severely impaired the ability of the PDGF-R cytoplasmic domain to associate with cellular substrates in vitro. This deletion also inhibited receptor and substrate phosphorylation, reduced the receptor's mitogenic activity, and completely abolished its oncogenic signaling potential. Surprisingly, removal of only six additional amino acids, including Tyr-989, restored substantial receptor and substrate phosphorylation capacity as well as transforming potential and yielded a receptor with wild-type levels of ligand-induced mitogenic activity. However, the ability of this chimera to bind phospholipase C gamma was severely impaired in comparison with the ability of the wild-type receptor, while the association with other cellular proteins was not affected. Further deletion of 35 residues, including Tyr-977, nearly abolished all PDGF-R cytoplasmic-domain biological signaling activities. None of the three C-terminal truncations completely abolished the mitogenic potential of the receptors or had any influence on ligand binding or receptor down regulation. Together, these data implicate the 80 C-terminal-most residues of the PDGF-R, and possibly Tyr-989, in phospholipase C gamma binding, while receptor sequences upstream from Asp-988 appear to be essential for specific interactions with other cellular polypeptides such as ras GTPase-activating protein and phosphatidylinositol 3-kinase. Thus, the mutants described here allow the separation of distinct PDGF-activated signaling pathways and demonstrate that phospholipase C gamma phosphorylation is not required for mitogenesis and transformation.

Biosynthetic and growth abnormalities are associated with high-level expression of CFTR in heterologous cells

1996 ◽  
Vol 270 (1) ◽  
pp. C341-C351 ◽  
Author(s):  
S. C. Schiavi ◽  
N. Abdelkader ◽  
S. Reber ◽  
S. Pennington ◽  
R. Narayana ◽  
...  
Keyword(s):  
Cell Growth ◽  
T Antigen ◽  
Permissive Temperature ◽  
Channel Activity ◽  
Wild Type ◽  
High Level Expression ◽  
Cl Channel ◽  
M Phase ◽  
High Level ◽  
Growth Abnormalities

An inducible gene amplification system was utilized to study the effects of overexpression of cystic fibrosis transmembrane conductance regulator (CFTR) in vitro. BTS, a monkey kidney cell line expressing a temperature-sensitive simian virus 40 (SV-40) large T antigen was stably transfected at the nonpermissive temperature with a plasmid containing an SV-40 origin of replication and the cDNA for either the wild-type CFTR or the mutant G551D-CFTR. Shift of the isolated cell lines to the permissive temperature resulted in induction and accumulation to high levels of the CFTR plasmid, mRNA, and protein. However, high-level expression of CFTR was transient in both BTS-CFTR and BTS-G551D cells due to a decrease in their respective levels of CFTR mRNA. Because G551D-CFTR only exhibits residual Cl channel activity, this suggests that the observed downregulation with BTS-G551D cells may have been induced by either the physical presence of high amounts of CFTR or some low threshold level of Cl- channel activity. Examination of cell growth properties revealed a correlation between high-level expression of wild-type CFTR and growth arrest of the cells at the G2/M phase. However, similar induction of the G551D-CFTR mutant showed only a slight growth inhibition and little enrichment of cells at the G2/M phase. Cytofluorographic analysis further revealed that BTS-CFTR cells were significantly larger than parental BTS or BTS-G551D cells at all stages of the cell cycle. These results indicate that CFTR overexpression is capable of inducing its own downregulation and that high levels of Cl- channel activity can result in increased cell volume and subsequent cell growth abnormalities.

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