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PubMed1988

Senile cardiac amyloidosis in senescence accelerated mouse (SAM).

The characteristics of the senescence accelerated mouse (SAM), a new murine model for accelerated senescence, are early senescence and a high incidence of senile amyloidosis. This study was performed to clarify histopathologically the details of senile cardiac amyloidosis in SAM, and the incidence of amyloidosis in the heart of SAM (-P) was 46.0% (1+: 22.0; 2+: 16.0; 3+: 8.0%). Amyloid infiltrated the ventricular walls, interventricular septum, atrial walls and interatrial septum. Amyloid deposition was prominent around the myocardial fibers and in the vascular walls. Amyloid involvement was greater in the veins than in the arteries. Senile cardiac amyloidosis of SAM was mild or moderate and not severe, in general. The age dependency of amyloidosis incidence of the heart was confirmed. The heart/body weight ratio tended to parallel the grade of cardiac amyloidosis. SAM often had complications such as abscess, lymphoma, skin ulcer, etc. The incidence of amyloidosis was higher in SAM with these complications than in SAM without them. The complications seemed to promote the progress of cardiac amyloidosis and to superimpose secondary amyloidosis. In SAM senile cardiac amyloidosis is less frequent than renal amyloidosis (64.4%) or hepatic amyloidosis (63.3%).

Abscess↗
PubMed1990

Effects of repeated administrations of facteur thymique sérique (FTS) on biochemical changes related to aging in senescence-accelerated mouse (SAM).

Superoxide dismutase (SOD) activity,malondialdehyde (MDA) content and monoamine oxidase B (MAO-B) activity were measured in the brain, liver and kidney of a normal aging strain (R/1) and an accelerating aging strain (P/8) senescence-accelerated mice (SAM) at 9-10 months of age, and the effects of facteur thymique sérique (FTS) were examined. The activity of Cu,Zn-SOD in the kidney and MAO-B in the liver was significantly low and high in SAM-P/8 compared to SAM-R/1. FTS enhanced the activity of Mn-SOD and Cu,Zn-SOD in the kidney of SAM-P/8 and Cu,Zn-SOD activity in the brain of both SAM-P/8 and SAM-R/1. It decreased the activity of MAO-B in the liver and the contents of malondialdehyde (MDA) in the brain and kidney of SAM-P/8. Thus, FTS affects the biochemical factors related to senescence in SAM-P/8, a particular senescent animal model, and may thus possibly be effective as an anti-senescent medicine.

Aging↗
PubMed2004

SAM(g2) analysis for detecting spike localization: a comparison with clinical symptoms and ECD analysis in an epileptic patient.

SAM(g2) analysis, a combination of synthetic aperture magnetometry (SAM) and excess kurtosis (g2) method, is a novel epilepsy analysis procedure based on a spatial filtering technique. By producing a three-dimensional image of the g2 values and superimposing them onto a patient's MR images, this analysis can automatically estimate spike localization from raw MEG epilepsy signals including spikes. The aim of this study is to examine SAM(g2) analysis using MEG signals of an epileptic patient, whose clinical symptoms of colored elementary visual auras had ceased in accordance with the changes of the estimated localizations of the equivalent current dipoles (ECDs) of the interictal spikes. His visual auras were experienced in 1997, while they ceased in 1999 with effective medication. The patient provided written informed consent for the experimental procedures. The MEG signals were recorded in 1997 and 1999, and were analyzed using both ECD and SAM(g2) analyses. For the MEG signals of 1997, ECD analysis estimated most of the interictal spikes in the right fusiform and inferior temporal gyri, which subserve human color processing. SAM(g2) analysis also estimated them in the same areas. For those of 1999, both ECD and SAM(g2) analyses estimated them in the right transverse gyrus of Heschl. As well as ECD analysis, SAM(g2) analysis successfully estimated the changes of the localizations of the interictal spikes in accordance with the changes of the patient's clinical symptoms, indicating that SAM(g2) analysis is useful for detection of interictal spike localization in epileptic patients.

Action Potentials↗
PubMed1989

Age-related changes in the temporomandibular joint of the senescence accelerated mouse. SAM-P/3 as a new murine model of degenerative joint disease.

Age-related changes of the condyle of the temporomandibular joint (TMJ) in strains of Senescence Accelerated Mouse (SAM) were investigated. With advancing age, all strains of SAM showed degenerative joint disease initiated by degenerative changes such as eg, roughness, fissure, and erosion on the condylar surface. These degenerative changes were in concert with an active remodeling that can lead to deformation of the condyle. Moreover, the short-lived SAM-P (accelerated senescence prone mouse) strains developed these degenerative changes earlier than did the SAM-R (accelerated senescence resistant mouse) strains. Thus, development of degenerative joint disease in SAM was closely related not only to chronological age but also to the accelerated senescence phenomenon. Of the SAM-P series, the SAM-P/3 strain was the first to manifest degenerative changes (approximately 50% at 7 to 9 months of age and 100% over 12 months of age) and thereafter showed the highest incidence of severe changes with overt deformity. As a model of degenerative joint disease, this strain of SAM should prove useful.

Aging↗
PubMed2006

Modulating cell adhesion and spreading by control of FnIII7-10 orientation on charged self-assembled monolayers (SAMs) of alkanethiolates.

In this work, we demonstrate that surface charge can be used to modulate cell adhesion/spreading through the control of the orientation of adsorbed FnIII(7-10), which is a cell-adhesive protein containing RGD residues. Carboxylic acid (COOH) and amine (NH(2))-terminated self-assembled monolayers (SAMs) of alkanethiolates were used as model negatively and positively charged surfaces, respectively. The adsorbed amount of FnIII(7-10) is controlled to be equivalent on both SAMs as confirmed by the adsorption isotherms determined using I(125)-radiolabeled FnIII(7-10.) The binding of a monoclonal antibody specific for the cell-binding domain of FnIII(7-10) was measured by surface plasmon resonance (SPR) to evaluate FnIII(7-10) orientations on different SAMs. Results indicate that adsorbed FnIII(7-10) on NH(2)-SAM has an orientation with more cell-binding domains accessible than on COOH-SAM, confirming our predictions from Monte Carlo simulations. Both phase contrast images and Vybrant MTT cell proliferation assays show that the adhesion/spreading of bovine aortic endothelial cells (BAECs) on the NH(2)-SAM is significantly better than that on the COOH-SAM coated with an equivalent amount of FnIII(7-10). These results indicate that surface charge can be used to specifically orient cell adhesive proteins such as FnIII(7-10), thus providing a promising strategy to increase the activity of materials incorporating biological moieties.

Alkanesulfonates↗
PubMed1994

A soluble form of K-sam/FGFR2 protein in the culture medium of human gastric cancer cells.

K-SAM/FGFR2 gene encodes a receptor tyrosine kinase which belongs to the fibroblast growth factor receptor family and is amplified and overexpressed in KATO-III gastric cancer cells. To characterize K-sam proteins in cancer cells, anti-K-sam rabbit polyclonal antibody PK1-2 was raised and used for the immunoprecipitation analysis. 135, 125, and 110-kDa transmembrane proteins were detected in KATO-III cell lysate, while a soluble truncated 85-kDa K-sam protein was found in the conditioned medium. The molecular size of the soluble K-sam protein does not match with those predicted from the secreted forms of the K-sam cDNA which have been cloned so far. The soluble K-sam protein was highly N-glycosylated like the transmembrane versions, and N-glycosylation appeared to be necessary for its release.

3T3 Cells↗
PubMed1989

Decreased endosteal formation during cortical bone modelling in SAM-P/6 mice with a low peak bone mass.

Inter-strain differences in bone mass and density during growth were followed in three strains of mice: SAM-P/2, SAM-R/1 and SAM-P/6 (a murine model of senile osteoporosis, Matsushita et al., Am J Pathol 1986;125:276-283). Photometrically, the inter-strain disparities first appeared in mice at about age 28 days and increased until age 60 days. During this period, tetracycline labelling revealed significant strain differences regarding rate of the appositional formation at the endosteal surface but not at the periosteal surface. The order coincided with results of the photometrical assay, that is, highest in SAM-P/2, followed by SAM-R/1 and SAM-P/6, respectively. Therefore, strain differences, especially the osteopenic state of SAM-P/6, occur, at least in part, by disparities in endosteal formation rates during cortical bone modelling.

Aging↗
PubMed2002

Stromal interaction molecule 1 (STIM1), a transmembrane protein with growth suppressor activity, contains an extracellular SAM domain modified by N-linked glycosylation.

Stromal interaction molecule 1 (STIM1) is a cell surface transmembrane glycoprotein implicated in tumour growth control and stromal-haematopoietic cell interactions. A single sterile alpha motif (SAM) protein-protein interaction domain is modelled within its extracellular region, a subcellular localisation not previously described for other SAM domain-containing proteins. We have defined the transmembrane topology of STIM1 by determining the sites of N-linked glycosylation. We have confirmed that STIM1 is modified by N-linked glycosylation at two sites within the SAM domain itself, deduced as asparagine residues N131 and N171, demonstrating that STIM1 is translocated across the membrane of the endoplasmic reticulum such that the SAM domain resides within the endoplasmic reticulum (ER) lumen. Both N-linked oligosaccharides remain endoglycosidase H-sensitive, indicating absence of full processing within the ER and Golgi. This immature modification is nevertheless sufficient and critical for cell surface expression of STIM1. We show that STIM1-STIM1 homotypic interactions are mediated via the cytoplasmic rather than the extracellular region of STIM1, excluding an essential role for the SAM domain in these protein interactions. These studies provide the first evidence for an extracellular localisation of a SAM domain within any protein, and the first example of a SAM domain modified by N-linked glycosylation.

Cloning, Molecular↗
PubMed2003

In vivo CH3(CH2)11SAu SAM electrodes in the beating heart: in situ analytical studies relevant to pacemakers and interstitial biosensors.

To study in vivo modification of the SAM equivalent circuit when a highly ordered SAM is used as a bioelectrode, dodecanethiolate SAM-Au intramuscular electrodes were studied in living rat heart in a challenging in situ perfused rat model by impedance spectroscopy, cyclic voltammetry, and neutron activation analysis (NAA). The SAM layer experienced disintegration in vivo biological system, as NAA detected the presence of Au atoms that had leached into the surrounding living tissue. Therefore, the underlying Au surface became exposed during biological implant. Study by impedance spectroscopy, however, revealed perfect capacitive behavior for the SAM, similar to in vitro behavior. Electrodes showed a pure capacitive Nyquist plot with 86.1-89.4 degrees near-vertical line segments as the equivalent circuit locus, as for a parallel plate capacitor. Impedance magnitude varied linearly with 1/omega excluding diffusionally limited ionic charge transport. There was no diffusional conductive element Z(W infinity ) or spatially confined Warburg impedance Z(D). The effect of in vivo exposure of a highly ordered SAM is a 'sealing over' effect of new defects by the binding of proteinaceous or lipid species in the biological milieu, a fact of significance for SAM electrodes used either as pacemaker electrodes or as a platform for in vivo biosensors.

Animals↗
PubMed1999

The crystal structure of an Eph receptor SAM domain reveals a mechanism for modular dimerization.

The sterile alpha motif (SAM) domain is a novel protein module of approximately 70 amino acids that is found in a variety of signaling molecules including tyrosine and serine/threonine protein kinases, cytoplasmic scaffolding and adaptor proteins, regulators of lipid metabolism, and GTPases as well as members of the ETS family of transcription factors. The SAM domain can potentially function as a protein interaction module through the ability to homo- and hetero-oligomerize with other SAM domains. This functional property elicits the oncogenic activation of chimeric proteins arising from translocation of the SAM domain of TEL to coding regions of the betaPDGF receptor, Abl, JAK2 protein kinase and the AML1 transcription factor. Here we describe the 2.0 A X-ray crystal structure of a SAM domain homodimer from the intracellular region of the EphA4 receptor tyrosine kinase. The structure reveals a mode of dimerization that we predict is shared amongst the SAM domains of the Eph receptor tyrosine kinases and possibly other SAM domain containing proteins. These data indicate a mechanism through which an independently folding protein module can form homophilic complexes that regulate signaling events at the membrane and in the nucleus.

Amino Acid Sequence↗
PubMed2001

Evaluation of protein multiple alignments by SAM-T99 using the BAliBASE multiple alignment test set.

MOTIVATION: SAM-T99 is an iterative hidden Markov model-based method for finding proteins similar to a single target sequence and aligning them. One of its main uses is to produce multiple alignments of homologs of the target sequence. Previous tests of SAM-T99 and its predecessors have concentrated on the quality of the searches performed, not on the quality of the multiple alignment. In this paper we report on tests of multiple alignment quality, comparing SAM-T99 to the standard multiple aligner, CLUSTALW. RESULTS: The paper evaluates the multiple-alignment aspect of the SAM-T99 protocol, using the BAliBASE benchmark alignment database. On these benchmarks, SAM-T99 is comparable in accuracy with ClustalW. AVAILABILITY: The SAM-T99 protocol can be run on the web at http://www.cse.ucsc.edu/research/compbio/HMM-apps/T99-query.html and the alignment tune-up option described here can be run at http://www.cse.ucsc.edu/research/compbio/HMM-apps/T99-tuneup.html. The protocol is also part of the standard SAM suite of tools. http://www.cse.ucsc.edu/research/compbio/sam/

Computational Biology↗
PubMed1994

Molecular genetic characterization of the senescence-accelerated mouse (SAM) strains.

Senescence-Accelerated Mouse (SAM) is a murine model of accelerated senescence, which consists of the senescence-prone P series and the senescence-resistant R series of strains. In order to characterize these SAM strains molecular genetically, we have performed a series of Southern hybridization experiments using oligonucleotide probes designed to recognize the endogenous mouse retrovirus sequences. The repertoires of endogenous retroviruses in different SAM strains indicated that each SAM strain is distinct. Comparisons of the SAM strains with the parental AKR/J strain revealed significant differences between them, suggesting the involvement of other strains in the course of the development of SAM. While some of the endogenous retroviruses were found in all of the SAM strains, others were found to be distributed uniquely, indicating their potential usefulness as genetic markers in the analysis of strain-specific phenotypes, and possibly of the phenomenon of accelerated senescence itself.

Aging↗
PubMed1986

Molecular cloning and nucleotide sequence of cDNA for murine senile amyloid protein: nucleotide substitutions found in apolipoprotein A-II cDNA of senescence accelerated mouse (SAM).

cDNA clones encoding the murine senile amyloid protein (ASSAM) have been isolated from animal models of accelerated senescence (SAM-P/1) and from normal aging (SAM-R/1). Immunochemical and protein sequence studies revealed that apolipoprotein (apo) A-II is a serum precursor of ASSAM. A 17-base synthetic oligonucleotide based on residues 39-44 of ASSAM was used as a hybridization probe for screening newly constructed SAM-P/1 and SAM-R/1 liver cDNA libraries. The structure of murine apo A-II cDNA is of interest because of the amino acid substitution found in ASSAM and serum apo A-II of SAM-P; in SAM-R or other random bred slc:ICR mice, amino acid residue 5 of mature apo A-II is proline but, in SAM-P, this amino acid is changed to glutamine. This amino acid replacement is caused by two nucleotide substitutions (CCA for proline codon to CAG for glutamine codon). The third base mutation may not be relevant to the substitution of amino acid. Attention is directed to the relation of this amino acid substitution to the specific deposition of apo A-II, as a tissue amyloid fibril.

Aging↗
PubMed1992

Inbred SAM-P/10 as a mouse model of spontaneous, inherited brain atrophy.

We developed a novel inbred strain of mouse with age-related brain atrophy and it was named "Senescence Accelerated Mouse (SAM)-P/10." Macroscopic morphometry indicated that the brains of SAM-P/10 showed age-dependent involutional changes mainly in the frontal portion of the cerebrum. The brain weight decreased by 8.6% throughout the life-span. There were no obvious defects in postnatal development. Semi-macroscopic morphometry revealed a prominent atrophy in the neocortex, olfactory cortex and amygdala. Microscopic morphometry showed that the neocortical neurons were lost with aging, with mostly the large neurons being affected which were lost by 35.6% throughout the life-span. Somata of the neocortical neurons shrank with advancing age. In a control SAM-R/1 strain with only a slight macroscopic involutional change in the brain without weight loss, neither loss of the neocortical large neurons nor shrinkage of the neocortical neurons was evident with aging. Learning and memory skills were evaluated using the one-trial passive avoidance task and conditional avoidance task. Young SAM-P/10 mice performed well in both tasks but older SAM-P/10 showed a poorer performance in both tasks, and this was even poorer than the performance of very old SAM-R/1 mice. Thus, SAM-P/10 can serve as a spontaneous animal model of brain atrophy for a variety of studies of aging of the brain. A better understanding of neurodegenerative diseases with dementia should be forthcoming.

Aging↗
PubMed2005

Polymerization of the SAM domain of MAPKKK Ste11 from the budding yeast: implications for efficient signaling through the MAPK cascades.

The sterile alpha-motif (SAM) is a protein module approximately 70 residues long and mainly involved in the protein-protein interactions of cell signaling and transcriptional repression. The SAM domain of the yeast MAPKKK Ste11 has a well-folded dimeric structure in solution. Interestingly, the well-folded dimer of the Ste11 SAM undergoes a time-dependent self-assembly upon lowering of the pH, leading to the formation of high molecular weight oligomers. The oligomeric structures rapidly disassemble to the well-folded dimer upon reversal of the pH to close to neutral conditions. Circular dichroism (CD) and atomic force microscopy (AFM) experiments demonstrate that the oligomeric structure formed at pH 5.0 appears to be highly helical and has architecture akin to proto-fibrils. Residue-specific kinetics of pH-triggered oligomerization obtained from real-time 15N-1H HSQC experiments indicate that the dimer-oligomer transition appears to involve all residues of the well-folded dimeric structure of the Ste11 SAM. Very interestingly, the interactions of the Ste11 and Ste50 SAM domains also lead to the formation of non-homogeneous hetero-complexes with significant populations of high molecular weight aggregates. AFM imaging shows that the Ste11-Ste50 hetero-polymeric aggregates assume the shapes of circular nano-particles with dimensions of 50-60 nano-meters (nm), in contrast to the proto-fibrils formed by the Ste11 SAM domain alone. Such intrinsic propensity for dimer to oligomer transition of the Ste50-binding SAM domain of Ste11 may endow the MAPKKK Ste11 with unique functional properties required for efficient and high fidelity signal transduction in the budding yeast.

Circular Dichroism↗
PubMed1999

Solution structure of the receptor tyrosine kinase EphB2 SAM domain and identification of two distinct homotypic interaction sites.

The sterile alpha motif (SAM) is a protein interaction domain of around 70 amino acids present predominantly in the N- and C-termini of more than 60 diverse proteins that participate in signal transduction and transcriptional repression. SAM domains have been shown to homo- and hetero-oligomerize and to mediate specific protein-protein interactions. A highly conserved subclass of SAM domains is present at the intracellular C-terminus of more than 40 Eph receptor tyrosine kinases that are involved in the control of axonal pathfinding upon ephrin-induced oligomerization and activation in the event of cell-cell contacts. These SAM domains appear to participate in downstream signaling events via interactions with cytosolic proteins. We determined the solution structure of the EphB2 receptor SAM domain and studied its association behavior. The structure consists of five helices forming a compact structure without binding pockets or exposed conserved aromatic residues. Concentration-dependent chemical shift changes of NMR signals reveal two distinct well-separated areas on the domains' surface sensitive to the formation of homotypic oligomers in solution. These findings are supported by analytical ultracentrifugation studies. The conserved Tyr932, which was reported to be essential for the interaction with SH2 domains after phosphorylation, is buried in the hydrophobic core of the structure. The weak capability of the isolated EphB2 receptor SAM domain to form oligomers is supposed to be relevant in vivo when the driving force of ligand binding induces receptor oligomerization. A formation of SAM tetramers is thought to provide an appropriate contact area for the binding of a low-molecular-weight phosphotyrosine phosphatase and to initiate further downstream responses.

Amino Acid Motifs↗
PubMed1989

Comodulation masking release using SAM tonal complex maskers: effects of modulation depth and signal position.

The purpose of this investigation was to examine two stimulus parameters that were reasoned to be of importance to comodulation masking release (CMR). The first was the degree of fluctuation, or depth of modulation, in the masker bands, and the second was the temporal position of the signal with respect to the modulations of the masker. The investigation began by demonstrating the efficacy of sinusoidally amplitude-modulated (SAM) tonal complex maskers in eliciting CMR. "Nine-band" maskers, 650 ms in duration, were constructed by adding together nine SAM tones spaced at 100-Hz intervals from 300 to 1100 Hz. The rate of modulation for each SAM tone was 10 Hz, and the depth of modulation was 100%. Using such maskers, it was shown that when the on-frequency SAM tone had a modulation depth of 100%, the threshold for a 250-ms, 700-Hz tone improved monotonically as the modulation depths of the flanking SAM tones increased from 0% to 100%. When the on-frequency SAM tone had a modulation depth of 63%, some listeners performed optimally when the flanking SAM tones also exhibited a modulation depth of 63%, whereas others performed best when the flankers had modulation depths of 100%. With regard to signal position, a typical CMR effect was observed when the signal, consisting of a train of three 50-ms, 700-Hz tone bursts, was placed in the dips of the on-frequency masker. However, when the signal was placed at the peaks of the envelope, an increase in masking was observed for a comodulated masker.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

The many faces of SAM.

Protein-protein interactions are essential for the assembly, regulation, and localization of functional protein complexes in the cell. SAM domains are among the most abundant protein-protein interaction motifs in organisms from yeast to humans. Although SAM domains adopt similar folds, they are remarkably versatile in their binding properties. Some identical SAM domains can interact with each other to form homodimers or polymers. In other cases, SAM domains can bind to other related SAM domains, to non-SAM domain-containing proteins, and even to RNA. Such versatility earns them functional roles in myriad biological processes, from signal transduction to transcriptional and translational regulation. In this review, we describe the structural basis of SAM domain interactions and highlight their roles in the scaffolding of protein complexes in normal and pathological processes.

Animals↗