Face perception: broken into parts

A recent study has shown that, using transcranial magnetic stimulation to stimulate an area of the visual cortex, the perception of face parts can be selectively and reversibly disrupted, while the perception of their arrangement is spared.     

Face to face: meaning, feeling and perception in Amazonian welcoming ceremonies

Some welcoming ceremonies practised by indigenous peoples of the Amazon have been considered events that enable the establishment of a social link between potential enemies. The studies do not, however, indicate how the shift from latent hostility to a social relationship occurs. They only refer to the 'magical act' produced through the significant exchange during the dialogues that take place at the key moment of the ceremony. Examining the perceptual interaction of the Candoshi welcoming ceremony and not merely the text of the dialogue, this article attempts to incorporate into the analysis the intensity of the affective dimension which governs these rituals, which can help to explain how such rituals provide the participants with the confidence to initiate a social relationship.     

Face perception is modulated by sexual preference

Face perception is mediated by a distributed neural system in the human brain . The response to faces is modulated by cognitive factors such as attention, visual imagery, and emotion ; however, the effects of gender and sexual orientation are currently unknown. We used fMRI to test whether subjects would respond more to their sexually preferred faces and predicted such modulation in the reward circuitry. Forty heterosexual and homosexual men and women viewed photographs of male and female faces and assessed facial attractiveness. Regardless of their gender and sexual orientation, all subjects similarly rated the attractiveness of both male and female faces. Within multiple, bilateral face-selective regions in the visual cortex, limbic system, and prefrontal cortex, similar patterns of activation were found in all subjects in response to both male and female faces. Consistent with our hypothesis, we found a significant interaction between stimulus gender and the sexual preference of the subject in the thalamus and medial orbitofrontal cortex, where heterosexual men and homosexual women responded more to female faces and heterosexual women and homosexual men responded more to male faces. Our findings suggest that sexual preference modulates face-evoked activation in the reward circuitry.     

A species-specific frequency filter through specific inhibition, not specific excitation

Many bushcrickets produce specific song spectra for acoustic communication. Song detection and/ or recognition may make use of such specificity. Where in the nervous system are the filters for song frequency situated? A peripheral tuning for song frequency typically does not exist. Auditory receptor cells of bushcrickets connect to local and ascending neurons in the prothoracic ganglion. One of the ascending neurons (1) may function as a frequency filter in a group of four related bushcrickets (genera Ancistrura, Barbitistes). The frequency response of ascending neuron 1 is species-specific roughly corresponding to the frequency of the conspecific male song. The species-specific tuning of the neuron is not brought about by specific excitation, but by specific inhibition. By eliminating this frequency-dependent and species-specific inhibition the former filter neuron is transformed into an unspecific broad-band neuron in all four species. Its tuning then does not differ from omega neuron 1, a local neuron which is rather unspecific for frequency. Also, the supra-threshold responses of ascending neuron 1, which are different in intact animals, are similar to each other and similar to omega neuron 1 following elimination of inhibition. Only ascending neuron 1 of Ancistrura retains some species-specific features at low frequencies. In conclusion, evolution changed inhibition, not excitation of a species-specific neuron.     

Autoantibodies against the catalytic domain of BRAF are not specific serum markers for rheumatoid arthritis

Background

Autoantibodies to the catalytic domain of v-raf murine sarcoma viral oncogene homologue B1 (BRAF) have been recently identified as a new family of autoantibodies involved in rheumatoid arthritis (RA). The objective of this study was to determine antibody responses to the catalytic domain of BRAF in RA and other autoimmune diseases. The association between RA-related clinical indices and these antibodies was also assessed.

Methodology/Principal Findings

The presence of autoantibodies to the catalytic domain of BRAF (anti-BRAF) or to peptide P25 (amino acids 656–675 of the catalytic domain of BRAF; anti-P25) was determined in serum samples from patients with RA, primary Sjögren''s syndrome (pSS), systemic lupus erythematosus (SLE), and healthy controls by using indirect enzyme-linked immunosorbent assays (ELISAs) based on the recombinant catalytic domain of BRAF or a synthesized peptide, respectively. Associations of anti-BRAF or anti-P25 with disease variables of RA patients were also evaluated. Our results show that the BRAF-specific antibodies anti-BRAF and anti-P25 are equally present in RA, pSS, and SLE patients. However, the erythrocyte sedimentation rate (ESR) used to detect inflammation was significantly different between patients with and without BRAF-specific antibodies. The anti-BRAF-positive patients were found to have prolonged disease, and active disease occurred more frequently in anti-P25-positive patients than in anti-P25-negative patients. A weak but significant correlation between anti-P25 levels and ESRs was observed (r = 0.319, p = 0.004).

Conclusions/Significance

The antibody response against the catalytic domain of BRAF is not specific for RA, but the higher titers of BRAF-specific antibodies may be associated with increased inflammation in RA.     

Elastin induces myofibrillogenesis via a specific domain, VGVAPG.

A hallmark of vascular smooth muscle cells (VSMCs) is their dynamic ability to assemble and disassemble contractile proteins into sarcomeric units depending upon their phenotypic state. This phenotypic plasticity plays an important role during vascular development and in obstructive vascular disease. Previously, we showed that the Elastin gene product, tropoelastin, activates myofibrillar organization of VSMCs. Recently, others have suggested that elastin does not have a direct signaling role but rather binds to and alters the interactions of other matrix proteins with their cognate receptors or disrupts the binding of growth factors and cytokines. In contrast, we provide evidence that tropoelastin directly regulates contractile organization of VSMCs. First, we show that a discrete domain within tropoelastin, VGVAPG, induces myofibrillogenesis in a time- and dose-dependent fashion. We confirm specificity using a closely related control peptide that fails to stimulate actin stress fiber formation. Second, the activity of VGVAPG is not affected by the presence or absence of other serum or matrix components. Third, both the elastin hexapeptide and tropoelastin stimulate actin polymerization through a common pertussis toxin-sensitive G protein pathway that activates RhoA-GTPase and results in the conversion of G to F actin. Collectively, these data support a model whereby the elastin gene product, signaling through the VGVAPG domain, directly induces VSMC myofibrillogenesis.     

Face or hand,not both: perceptual correlates of reafferentation in a former amputee

The topography of the somatosensory maps of our body can be largely shaped by alterations of peripheral sensory inputs. Following hand amputation, the hand cortical territory becomes responsive to facial cutaneous stimulation. Amputation-induced remapping, however, reverses after transplantation, as the grafted hand (re)gains its sensorimotor representation. Here, we investigate hand tactile perception in a former amputee by touching either grafted hand singly or in combination with another body part. The results showed that tactile sensitivity recovered rapidly, being remarkably good 5 months after transplant. In the right grafted hand, however, the newly acquired somatosensory awareness was strikingly hampered when the ipsilateral face was touched simultaneously, i.e., right face perception extinguished right hand perception. Ipsilateral face-hand extinction was present in the formerly dominant right hand 5 months after transplant and eventually disappeared 6 months afterwards. Control conditions' results showed that right hand tactile awareness was not extinguished either by contralateral left face and left hand stimulation or ipsilateral stimulation of the arm, which is bodily close to, but cortically far from, the hand. We suggest that ipsilateral face-hand extinction is a perceptual counterpart of the remapping that occurs after allograft and eyewitnesses the inherently competitive nature of sensory representations.     

The beta1 integrin subunit is not a specific component of the costamere domain in human myocardial cells

Studies on altered integrin receptor expression during cardiac hypertrophy and heart failure requires accurate knowledge of the distributional pattern of integrins in myocardial cells. At present the general consensus is that in cardiac muscle the ₁ integrin receptor is mainly localized to the same sarcolemmal domain as vinculin at Z-band levels (costamere). Since most previous studies have been focusing on myocardial integrin distribution in lower mammals, the myocardial localization of the ₁ integrin subunit was investigated in biopsies collected from the auricle of patients undergoing a coronary bypass operation. Non-invasive serial optical sectioning was carried out by immuno-laser scanning confocal microscopy. Double-labelling for vinculin/-actinin, and the cytoplasmic domain for the ₁ integrin subunit, showed that ₁ integrin is deposited throughout both the vinculin/-actinin domains and the non-vinculin/-actinin domains. These results were supported by a semi-quantitative analysis in extended focus images of the latter preparations. Higher magnification views at the electron microscopical levels of the large, extracellular domain of the ₁ integrin subunit disclosed a pronounced labelling in the form of a dense, irregular punctuate pattern that was distributed at Z-disc domains as well as along the entire sarcolemmal area between Z-discs. Our findings show that in human, myocardial cells, the ₁ integrin receptor does not only localize to the surface membrane at the Z-disc level (costamere in cardiac muscle), but has a widespread distribution along the sarcolemma.     

Tissue-type specific systemin perception and the elusive systemin receptor

Systemin is a wound signaling peptide from tomato that is important for plant defenses against herbivory. The systemin receptor was initially identified as the tomato homolog of the brassinosteroid receptor BRI1, but genetic evidence argued against this finding. However, we found that BRI1 may function as an inappropriate systemin binding protein that does not activate the systemin signaling pathway. Here we provide evidence that systemin perception is localized in a tissue-type specific manner. Mesophyll protoplasts were not sensitive to systemin, while they responded to other elicitors. We hypothesize that the elusive systemin receptor is a protein with high similarity to BRI1 which is specifically localized in vascular tissue like the systemin precursor prosystemin. Binding of systemin to BRI1 may be an artifact of transgenic BRI1-overexpressing plants, but does not take place in wild type tomato cells.Key words: systemin, systemin receptor, brassinosteroids, BRI1, BRL, protoplastsSystemin is thought to be processed from its precursor prosystemin upon insect attack and wounding of tomato leaves. Strong evidence has been gathered for an important role of (pro-)systemin in the activation of defenses against insects, and the underlying signaling pathway has been studied in detail.¹ However, the perception of systemin is controversial. Meindl et al.² and Scheer and Ryan³ identified high affinity, saturable, reversible and specific cell surface binding sites on Solanum peruvianum suspension-cultured cells which are known to be highly sensitive to systemin.⁴ A purification approach using a photoaffinity systemin analog identified a 160 kDa protein as the systemin receptor (SR160).⁵ Follow-up studies showed that overexpression of tomato 35S::SR160 in systemin-insensitive tobacco plants conferred systemin sensitivity to tobacco.⁶ Surprisingly, SR160 turned out to be the tomato homolog of the brassinosteroid receptor BRI1,⁷ which raised many questions as to the functionality of a receptor for two structurally and functionally diverse ligands. It was then shown in two independent papers that a null mutant for tomato BRI1, cu-3, exhibited a normal response to systemin.^8,9 This was strong evidence that SR160/BRI1 does not represent the functional systemin receptor. Our recent data added a peculiar twist to this story. We found that overexpression of tomato BRI1 in tobacco suspension-cultured cells resulted in binding of a fluorescently labeled systemin to the plasma membranes of the transgenic tobacco cells, but not to wild type cells. Surprisingly, this did not result in BRI1-dependent signal transduction and activation of a defense response, although we detected weak BRI1-independent signaling responses to systemin.¹⁰ Together with the identification of BRI1 as the systemin receptor by Scheer and Ryan,⁵ the simplest explanation for this phenomenon is that BRI1 is a systemin binding protein, but not the physiological systemin receptor.Therefore and for other reasons, we suggested that the true systemin receptor may be a protein with very similar properties as BRI1, e.g., a homolog of the BRI1-like (BRL) proteins. The purification strategy employed by Scheer and Ryan5 may have resulted in binding of a photoaffinity-systemin derivative to BRI1 and one or more BRL proteins. Since BRLs and BRI1 have a very similar MW, multiple bands on a SDS-PAGE would not be detectable.Here, we would like to add another aspect of systemin perception. We provide evidence for tissue-specific systemin sensitivity and discuss how this may affect systemin binding to BRI1 and the elusive systemin receptor. Prosystemin is only present in phloem parenchyma cells.¹¹ It can be surmised that the systemin receptor is located close to these cells. Systemin perception results in JA synthesis in companion cells of vascular bundles.¹² Since JA or a JA derivative is the most likely phloem-mobile candidate for a systemic long-distance wound signal, it is thought that JA is moving from companion cells into sieve cells to reach distant parts of the plant for upregulation of wound response genes in leaf cells, including mesophyll cells.^13–15Here, we tested the hypothesis that mesophyll cells lack systemin perception. We generated mesophyll protoplasts from tomato leaf material as well as protoplasts from S. peruvianum suspension-cultured cells, the same cell line that had been used for the purification of SR160/BRI1 and is known to be highly sensitive to systemin. Mesophyll protoplasts showed increased phosphorylation of MAP kinases (MPKs) in response to the elicitors flg22 and chitosan, bacterial and fungal MAMPs, respectively. However, they did not respond to systemin. In contrast, the S. peruvianum protoplasts did respond to systemin and to flg22, demonstrating that the protoplasting procedure did not compromise the systemin perception mechanism (Fig. 1). Immunocomplex kinase assays with specific antibodies against tomato MPK2 produced similar results (data not shown). Since flg22, chitosan and systemin activated the same MPKs (Fig. 1), our data indicate that systemin perception is absent in mesophyll protoplasts. Our leaf protoplasting protocol is a modification of the protocol by Yoo et al. which results in the generation of mesophyll protoplasts.¹⁶ In contrast, suspension-cultured cells do not normally represent specific cell types and it is not known why the S. peruvianum cells are highly sensitive to systemin.Open in a separate windowFigure 1Absence of systemin-induced MPK phosphorylation in mesophyll cells. Protoplasts were generated (protocol available upon request) from S. peruvianum suspension-cultured cells and from S. lycopersicum cv. MicroTom leaves. After a 1.5 hour recovery phase on ice, protoplasts were resuspended in WI medium (0.5 M mannitol, 5 mM ME S pH 5.7, 20 mM KCl), recovered for 1 hour in non-stick tubes with constant rotation on a rotary shaker at room temperature, and then treated with either water (con), 10 nM systemin (sys), 100 nM flg22, or 2.5 µg/ml chitosan (from crab shells—chi) for 10 min at room temperature. Protoplasts were analyzed for MPK phosphorylation by immunoblotting using an anti-phospho-ER K antibody (phospho-p44/42 MA PK (Erk1/2) (Thr202/Tyr204); D13.14.4E; Cell Signaling Technology) at a dilution of 1:2,000. This antibody recognizes MPKs that are phosphorylated on either the Thr and Tyr or on only the Thr within the TE Y phosphorylation motif which is conserved among plant and metazoan MPKs. It is known to recognize the tobacco MPKs SIPK and WIPK²¹ and Arabidopsis MPK6 and MPK3,²² the orthologs of tomato MPK1/2 and MPK3.²³ Bands were visualized as described.¹⁰ Proteins on membranes were stained with Ponceau S to demonstrate equal loading.Intriguingly, BRL1, BRL2 and BRL3 are expressed in the vasculature and function in vascular pattern formation in Arabidopsis, while BRI1 is ubiquitously expressed in dividing and elongating cells. BRL3 is even specifically expressed in phloem cells.¹⁷ This matches the highly specific localization of prosystemin in the phloem parenchyma cells.^11,18 The highest BRI1 expression is found in growing parts of young leaves^17,19 while prosystemin is specifically present in the phloem parenchyma cells throughout all developmental stages.¹¹ In this context, it is also interesting to note that application of systemin to tomato plants via the cut stem results in rapid and strong MPK activation. In this assay, systemin is delivered to leaf cells via the transpiration stream and therefore present in vascular tissue.²⁰Based on the combined evidence, we propose that the true systemin receptor is a BRL or similar protein which is expressed in phloem cells in the vicinity of the parenchyma cells that express prosystemin, but not in mesophyll cells. Because of the similarity between BRLs and BRI1, BRI1 was erroneously identified as the systemin receptor. Inappropriate binding of systemin to BRI1 is consistent with the high similarity between BRI1 and BRLs. However, because of the tissue-specificity of the systemin signaling pathway, inappropriate binding of systemin to BRI1 may rarely occur in wild type plants and may not pose an interference problem for either systemin or brassinosteroid signaling.     

Specific collagenolysis by gelatinase A, MMP-2, is determined by the hemopexin domain and not the fibronectin-like domain

In view of the essential role of the hemopexin domain of the traditional interstitial collagenases, MMP-1, -8, -13 and MT1-MMP (MMP-14), in determining specific collagen cleavage we have studied the function of this domain in MMP-2, relative to that of the fibronectin-like domain that promotes gelatinolysis. Although the fibronectin-like domain promotes avid binding to collagen, our data demonstrate that the catalytic and hemopexin domains of MMP-2 are sufficient to effect the critical step in cleavage of rat type I collagen into 3/4 and 1/4 fragments. The mechanism of MMP-2 cleavage of collagen proceeds in two phases, the first resembling that of the interstitial collagenases, followed by gelatinolysis, promoted by the fibronectin-like domain.     

The CEACAM1 transmembrane domain, but not the cytoplasmic domain, directs internalization of human pathogens via membrane microdomains

Several bacterial pathogens exploit carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) to promote attachment and uptake into eukaryotic host cells. The widely expressed isoform CEACAM1 is involved in cell–cell adhesion, regulation of cell proliferation, insulin homeostasis, and neo-angiogenesis, processes that depend on the cytoplasmic domain of CEACAM1. By analysing the molecular requirements for CEACAM1-mediated internalization of bacteria, we surprisingly find that the CEACAM1 cytoplasmic domain is completely obsolete for bacterial uptake. Accordingly, CEACAM1-4L as well as a CEACAM1 mutant with a complete deletion of the cytoplasmic domain (CEACAM1 ΔCT) promote equivalent internalization of several human pathogens. CEACAM1-4L- and CEACAM1 ΔCT-mediated uptake proceeds in the presence of inhibitors of actin microfilament dynamics, which is in contrast to CEACAM3-mediated internalization. Bacteria-engaged CEACAM1-4L and CEACAM1 ΔCT, but not CEACAM3, localize to a gangliosid GM1- and GPI-anchored protein-containing portion of the plasma membrane. In addition, interference with cholesterol-rich membrane microdomains severely blocks bacterial uptake via CEACAM1-4L and CEACAM1 ΔCT, but not CEACAM3. Similar to GPI-anchored CEACAM6, both CEACAM1-4L as well as CEACAM1 ΔCT partition into a low-density, Triton-insoluble membrane fraction upon receptor clustering, whereas CEACAM3 is not detected in this fraction. Bacterial uptake by truncated CEACAM1 or chimeric CEACAM1/CEACAM3 molecules reveals that the transmembrane domain of CEACAM1 is responsible for its association with membrane microdomains. Together, these data argue for a functional role of lipid rafts in CEACAM1-mediated endocytosis that is promoted by the transmembrane domain of the receptor and that might be relevant for CEACAM1 function in physiologic settings.     

Apoptosis induced by human Fas-associated factor 1, hFAF1, requires its ubiquitin homologous domain, but not the Fas-binding domain

FAF1 is a Fas-binding protein without typical death domain. Instead, FAF1 has several domains found in proteins of ubiquitination pathway. Transient overexpression of hFAF1 in BOSC23 cells caused membrane blebbing and cell body condensation which were characteristics of apoptosis. Subsequent analysis revealed that overexpression of hFAF1 induced nuclear condensation, appearance of phosphatidylserines in the outer leaflet of the cellular membrane, and caspase 3 activation. The apoptotic potential of hFAF1 required downstream ubiquitin homologous domain (UB2) and adjacent nuclear localization signal but not the Fas-binding domain. Our data showed that mere intrinsic overexpression of hFAF1 initiated apoptosis in the absence of any extrinsic death signal in BOSC23 cells.     

Dusty protein kinases: primary structure, gene evolution, tissue specific expression and unique features of the catalytic domain

Ser/Thr- and Tyr-Protein kinases constitute a key switch underlying the dynamic nature and graded regulation of signal transduction and pathway activities in cellular organization. Here we describe the identification and characterization of Dusty, a single-copy gene that arose in metazoan evolution and encodes a putative dual Ser/Thr and Tyr protein kinase with unique structural features. Dusty is widely expressed in vertebrates, broadly distributed in the central nervous system, and deregulated in certain human cancers. Confocal imaging of transiently expressed human Dusty-GFP fusion proteins showed a cytoplasmic distribution. Dusty proteins from lower to higher species display an increasing degree of sequence conservation from the N-terminal non-catalytic domain to C-terminal catalytic domain. The non-catalytic region has eight conserved cysteine residues, multiple potential kinase-docking motifs and phosphorylation sites, whereas the catalytic domain is divergent and about equally distant of Ser/Thr and Tyr protein kinases. Homology analyses identified the essential catalytic residues, suggesting that Dusty homologues all possess the enzymatic activity of a protein kinase. Taken together, Dusty is a unique evolutionarily selected group of divergent protein kinases that may play important functional roles in the brain and other tissues of vertebrates.     

Distinctive features of Drosophila alternative splicing factor RS domain: implication for specific phosphorylation, shuttling, and splicing activation

The human splicing factor 2, also called human alternative splicing factor (hASF), is the prototype of the highly conserved SR protein family involved in constitutive and regulated splicing of metazoan mRNA precursors. Here we report that the Drosophila homologue of hASF (dASF) lacks eight repeating arginine-serine dipeptides at its carboxyl-terminal region (RS domain), previously shown to be important for both localization and splicing activity of hASF. While this difference has no effect on dASF localization, it impedes its capacity to shuttle between the nucleus and cytoplasm and abolishes its phosphorylation by SR protein kinase 1 (SRPK1). dASF also has an altered splicing activity. While being competent for the regulation of 5' alternative splice site choice and activation of specific splicing enhancers, dASF fails to complement S100-cytoplasmic splicing-deficient extracts. Moreover, targeted overexpression of dASF in transgenic flies leads to higher deleterious developmental defects than hASF overexpression, supporting the notion that the distinctive structural features at the RS domain between the two proteins are likely to be functionally relevant in vivo.     

Age dependent dispersal is not a simple process: Density dependence, stability, and chaos

I present both discrete and continuous models for a single species with overlapping generations, density dependence, and movement rates that vary with age. In the discrete time and space model, I show that if the strongly density dependent age class(es) are stationary, the spatially structured model may exhibit instabilities or even chaos which are not present in the corresponding model without spatial structure. I argue that the conditions which lead to these diffusive instabilities are likely to be met in natural populations. Thus it is important to consider the interaction between age structure and spatial structure in both experimental and theoretical work. In particular, the conditions leading to chaos are more common than would be predicted in models which ignore structure.     

The mGluR6 ligand-binding domain,but not the C-terminal domain,is required for synaptic localization in retinal ON-bipolar cells

Signals from retinal photoreceptors are processed in two parallel channels—the ON channel responds to light increments, while the OFF channel responds to light decrements. The ON pathway is mediated by ON type bipolar cells (BCs), which receive glutamatergic synaptic input from photoreceptors via a G-protein-coupled receptor signaling cascade. The metabotropic glutamate receptor mGluR6 is located at the dendritic tips of all ON-BCs and is required for synaptic transmission. Thus, it is critically important for delivery of information from photoreceptors into the ON pathway. In addition to detecting glutamate, mGluR6 participates in interactions with other postsynaptic proteins, as well as trans-synaptic interactions with presynaptic ELFN proteins. Mechanisms of mGluR6 synaptic targeting and functional interaction with other synaptic proteins are unknown. Here, we show that multiple regions in the mGluR6 ligand-binding domain are necessary for both synaptic localization in BCs and ELFN1 binding in vitro. However, these regions were not required for plasma membrane localization in heterologous cells, indicating that secretory trafficking and synaptic localization are controlled by different mechanisms. In contrast, the mGluR6 C-terminus was dispensable for synaptic localization. In mGluR6 null mice, localization of the postsynaptic channel protein TRPM1 was compromised. Introducing WT mGluR6 rescued TRPM1 localization, while a C-terminal deletion mutant had significantly reduced rescue ability. We propose a model in which trans-synaptic ELFN1 binding is necessary for mGluR6 postsynaptic localization, whereas the C-terminus has a role in mediating TRPM1 trafficking. These findings reveal different sequence determinants of the multifunctional roles of mGluR6 in ON-BCs.