Preventing apoptotic cell death by a novel small heat shock protein

Expression Levels of GHRH-Receptor, pAkt and Hsp90 Predict 10-Year Overall Survival in Patients with Locally Advanced Rectal Cancer

Background: Rectal cancer constitutes nearly one-third of all colorectal cancer diagnoses, and certain clinical and molecular markers have been studied as potential prognosticators of patient survival. The main objective of our study was to investigate the relationship between the expression intensities of certain proteins, including growth-hormone-releasing hormone receptor (GHRH-R), Hsp90, Hsp16.2, p-Akt and SOUL, in specimens of locally advanced rectal cancer patients, as well as the time to metastasis and 10-year overall survival (OS) rates. We also investigated whether these outcome measures were associated with the presence of other clinical parameters. Methods: In total, 109 patients were investigated retrospectively. Samples of pretreatment tumors were stained for the proteins GHRH-R, Hsp90, Hsp16.2, p-Akt and SOUL using immunhistochemistry methods. Kaplan–Meier curves were used to show the relationships between the intensity of expression of biomarkers, clinical parameters, the time to metastasis and the 10-year OS rate. Results: High levels of p-Akt, GHRH-R and Hsp90 were associated with a significantly decreased 10-year OS rate (p = 0.001, p = 0.000, p = 0.004, respectively) and high expression levels of p-Akt and GHRH-R were correlated with a significantly shorter time to metastasis. Tumors localized in the lower third of the rectum were linked to both a significantly longer time to metastasis and an improved 10-year OS rate. Conclusions: Hsp 90, pAkt and GHRH-R as well as the lower-third localization of the tumor were predictive of the 10-year OS rate in locally advanced rectal cancer patients. The GHRH-R and Hsp90 expression levels were independent prognosticators of OS. Our results imply that GHRH-R could play a particularly important role both as a molecular biomarker and as a target for the anticancer treatment of advanced rectal cancer.

The Small Heat Shock Protein, HSPB1, Interacts with and Modulates the Physical Structure of Membranes

Small heat shock proteins (sHSPs) have been demonstrated to interact with lipids and modulate the physical state of membranes across species. Through these interactions, sHSPs contribute to the maintenance of membrane integrity. HSPB1 is a major sHSP in mammals, but its lipid interaction profile has so far been unexplored. In this study, we characterized the interaction between HSPB1 and phospholipids. HSPB1 not only associated with membranes via membrane-forming lipids, but also showed a strong affinity towards highly fluid membranes. It participated in the modulation of the physical properties of the interacting membranes by altering rotational and lateral lipid mobility. In addition, the in vivo expression of HSPB1 greatly affected the phase behavior of the plasma membrane under membrane fluidizing stress conditions. In light of our current findings, we propose a new function for HSPB1 as a membrane chaperone.

IFT25 is required for the construction of the trypanosome flagellum

Intraflagellar transport (IFT), the movement of protein complexes responsible for the assembly of cilia and flagella, is remarkably conserved from protists to humans. However, two IFT components (IFT25 and IFT27) are missing from multiple unrelated eukaryotic species. In mouse, IFT25 (also known as HSPB11) and IFT27 are not required for assembly of several cilia with the noticeable exception of the flagellum of spermatozoa. Here, we show that the Trypanosoma brucei IFT25 protein is a proper component of the IFT-B complex and displays typical IFT trafficking. By performing bimolecular fluorescence complementation assays, we reveal that IFT25 and IFT27 interact within the flagellum in live cells during the IFT process. IFT25-depleted cells construct tiny disorganised flagella that accumulate IFT-B proteins (with the exception of IFT27, the binding partner of IFT25) but not IFT-A proteins. This phenotype is comparable to the one following depletion of IFT27 and shows that IFT25 and IFT27 constitute a specific module that is necessary for proper IFT and flagellum construction in trypanosomes. Possible reasons why IFT25 and IFT27 would be required for only some types of cilia are discussed.

Heat shock proteins are differentially expressed in brain and spinal cord: implications for multiple sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease characterized by demyelination, inflammation and neurodegeneration throughout the central nervous system. Although spinal cord pathology is an important factor contributing to disease progression, few studies have examined MS lesions in the spinal cord and how they differ from brain lesions. In this study we have compared brain and spinal cord white (WM) and grey (GM) matter from MS and control tissues, focusing on small heat shock proteins (HSPB) and HSP16.2. Western blotting was used to examine protein levels of HSPB1, HSPB5, HSPB6, HSPB8 and HSP16.2 in brain and spinal cord from MS and age-matched non-neurological controls. Immunohistochemistry was used to examine expression of the HSPs in MS spinal cord lesions and controls. Expression levels were quantified using ImageJ. Western blotting revealed significantly higher levels of HSPB1, HSPB6 and HSPB8 in MS and control spinal cord compared to brain tissues. No differences in HSPB5 and HSP16.2 protein levels were observed, although HSPB5 protein levels were higher in brain WM versus GM. In MS spinal cord lesions, increased HSPB1 and HSPB5 expression was observed in astrocytes, and increased neuronal expression of HSP16.2 was observed in normal-appearing GM and type 1 GM lesions. The high constitutive expression of several HSPBs in spinal cord and increased expression of HSPBs and HSP16.2 in MS illustrate differences between brain and spinal cord in health and upon demyelination. Regional differences in HSP expression may reflect differences in astrocyte cytoskeleton composition and influence inflammation, possibly affecting the effectiveness of pharmacological agents.

Transcriptional and Translational Relationship in Environmental Stress: RNAseq and ITRAQ Proteomic Analysis Between Sexually Reproducing and Parthenogenetic Females in Moina micrura

Moina micrura is a kind of small-bodied water flea within the family Moinidae. Similar to Daphnia, M. micrura could also switch its reproduction mode from parthenogenetic female (PF) to sexual female (SF) to adapt to the external environment. To uncover the mechanisms of reproductive switching in M. micrura, we used both RNA-Seq and iTRAQ analyses to investigate the differentially expressed genes (DEGs) and their protein products between SF and PF in M. micrura. A total of 1665 DEGs (702 up-regulated, 963 down-regulated) and 600 differentially expressed proteins (DEPs) (102 up-regulated, 498 down-regulated) were detected in SF. Correlation analyses indicated that 31 genes were expressed significantly differentially at both transcriptomic and proteomic levels, including 15 up-regulated genes and 16 down-regulated genes in SF. Meanwhile, our data also showed that 528 DEPs have discordant expression at transcript level, implying post-transcriptional (including translational) regulation. These top up-regulated genes and their protein products in SF were mainly grouped into the globin-related family, vitellogenin-related family, cuticle-related family, Hsp-related family and methyltransferases-related family, which were all involved in the reproductive switching in Daphnia. In contrast, a cluster of orthologous groups revealed that up-regulated genes and their protein products in PF were strongly associated with the metabolic process, which may be responsible for rapid population proliferation in M. micrura.

IFT25, an intraflagellar transporter protein dispensable for ciliogenesis in somatic cells, is essential for sperm flagella formation

Intraflagellar transport (IFT) is a conserved mechanism essential for the assembly and maintenance of most eukaryotic cilia and flagella. However, IFT25, a component of the IFT complex, is not required for the formation of cilia in somatic tissues. In mice, the gene is highly expressed in the testis, and its expression is upregulated during the final phase when sperm flagella are formed. To investigate the role of IFT25 in sperm flagella formation, the gene was specifically disrupted in male germ cells. All homozygous knockout mice survived to adulthood and did not show any gross abnormalities. However, all homozygous knockout males were completely infertile. Sperm numbers were reduced and these sperm were completely immotile. Multiple morphological abnormalities were observed in sperm, including round heads, short and bent tails, with some tails showing branched flagella and others with frequent abnormal thicknesses, as well as swollen tips of the tail. Transmission electron microscopy revealed that flagellar accessory structures, including the fibrous sheath and outer dense fibers, were disorganized, and most sperm had also lost the "9+2" microtubule structure. In the testis, IFT25 forms a complex with other IFT proteins. In Ift25 knockout testes, IFT27, an IFT25 binding partner, was missing, and IFT20 and IFT81 levels were also reduced. Our findings suggest that IFT25, although not necessary for the formation of cilia in somatic cells, is indispensable for sperm flagellum formation and male fertility in mice.

Analysis of HspB1 (Hsp27) Oligomerization and Phosphorylation Patterns and Its Interaction with Specific Client Polypeptides

Human HspB1 (also denoted as Hsp27) belongs to the family of small (or stress) proteins (sHsps). The family, which contains ten members including αA,B-crystallin polypeptides, is characterized by a conserved C-terminal α-crystallin domain and molecular weights ranging from 20 to 40 kDa. Here, procedures are described for analyzing the dynamic oligomerization and phosphorylation patterns of HspB1 in cells exposed to different environments. Changes in the structural organization of HspB1 can reprogram its interaction with specific partner/client polypeptides. Methods are presented to analyze these interactions using tissue culture cells genetically modified to express different levels of this protein. In addition, the laboratory approaches presented here could be used to test the nine other human sHsp members as well as sHsps from other species.

Possible Predictive Markers of Response to Therapy in Esophageal Squamous Cell Cancer

The aim of the present study was to investigate the relationship between the intensity of biomarker expression and the response to radiochemotherapy in patients with advanced esophageal squamous cell cancer (ESCC). Ninety-two patients with locally advanced ESCC were examined retrospectively. Pre-treatment tumor samples were stained for proteins SOUL, Hsp 16.2, Growth Hormone-Releasing Hormone Receptor (GHRH-R) and p-Akt using immunhistochemistry methods. Kaplan-Meier curves were used to show the relationship between intensity of expression of biomarkers and clinical parameters and 3-year OS. A significant correlation was found between high intensity staining for Hsp 16.2, p-Akt and SOUL and poor response to NRCT. Application of a higher dose of radiation and higher dose of cisplatin resulted in better clinical and histopathological responses, respectively. Among the clinical parameters, the localization of the tumor in the upper-third of the esophagus and less than 10% weight loss were independent prognostic factors for increased 3-year OS. Hsp16.2, p-Akt and SOUL are predictors of negative response to NRCT, therefore these biomarkers may become promising targets for therapy. Furthermore, level of expression of p-Akt, weight loss and the localization of the tumor are significant factors in the prediction of OS in ESCC.

Upregulation and phosphorylation of HspB1/Hsp25 and HspB5/αB-crystallin after transient middle cerebral artery occlusion in rats

Ischemic stroke leads to cellular dysfunction, cell death, and devastating clinical outcomes. The cells of the brain react to such a cellular stress by a stress response with an upregulation of heat shock proteins resulting in activation of endogenous neuroprotective capacities. Several members of the family of small heat shock proteins (HspBs) have been shown to be neuroprotective. However, yet no systematic study examined all HspBs during cerebral ischemia. Here, we performed a comprehensive comparative study comprising all HspBs in an animal model of stroke, i.e., 1 h transient middle cerebral artery occlusion followed by 23 h of reperfusion. On the mRNA level out of the 11 HspBs investigated, HspB1/Hsp25, HspB3, HspB4/αA-crystallin, HspB5/αB-crystallin, HspB7/cvHsp, and HspB8/Hsp22 were significantly upregulated in the peri-infarct region of the cerebral cortex of infarcted hemispheres. HspB1 and HspB5 reached the highest mRNA levels and were also upregulated at the protein level, suggesting that these HspBs might be functionally most relevant. Interestingly, in the infarcted cortex, both HspB1 and HspB5 were mainly allocated to neurons and to a lesser extent to glial cells. Additionally, both proteins were found to be phosphorylated in response to ischemia. Our data suggest that among all HspBs, HspB1 and HspB5 might be most important in the neuronal stress response to ischemia/reperfusion injury in the brain and might be involved in neuroprotection.

HspB5/αB-crystallin increases dendritic complexity and protects the dendritic arbor during heat shock in cultured rat hippocampal neurons

The small heat shock protein ΗspΒ5 (αB-crystallin) exhibits generally cytoprotective functions and possesses powerful neuroprotective capacity in the brain. However, little is known about the mode of action of ΗspΒ5 or other members of the HspB family particularly in neurons. To get clues of the neuronal function of HspBs, we overexpressed several HspBs in cultured rat hippocampal neurons and investigated their effect on neuronal morphology and stress resistance. Whereas axon length and synapse density were not affected by any HspB, dendritic complexity was enhanced by HspB5 and, to a lesser extent, by HspB6. Furthermore, we could show that this process was dependent on phosphorylation, since a non-phosphorylatable mutant of HspB5 did not show this effect. Rarefaction of the dendritic arbor is one hallmark of several neurodegenerative diseases. To investigate if HspB5, which is upregulated at pathophysiological conditions, might be able to protect dendrites during such situations, we exposed HspB5 overexpressing neuronal cultures to heat shock. HspB5 prevented heat shock-induced rarefaction of dendrites. In conclusion, we identified regulation of dendritic complexity as a new function of HspB5 in hippocampal neurons.

Involvement of small heat shock proteins, trehalose, and lipids in the thermal stress management in Schizosaccharomyces pombe

Changes in the levels of three structurally and functionally different important thermoprotectant molecules, namely small heat shock proteins (sHsps), trehalose, and lipids, have been investigated upon heat shock in Schizosaccharomyces pombe. Both α-crystallin-type sHsps (Hsp15.8 and Hsp16) were induced after prolonged high-temperature treatment but with different kinetic profiles. The shsp null mutants display a weak, but significant, heat sensitivity indicating their importance in the thermal stress management. The heat induction of sHsps is different in wild type and in highly heat-sensitive trehalose-deficient (tps1Δ) cells; however, trehalose level did not show significant alteration in shsp mutants. The altered timing of trehalose accumulation and induction of sHsps suggest that the disaccharide might provide protection at the early stage of the heat stress while elevated amount of sHsps are required at the later phase. The cellular lipid compositions of two different temperature-adapted wild-type S. pombe cells are also altered according to the rule of homeoviscous adaptation, indicating their crucial role in adapting to the environmental temperature changes. Both Hsp15.8 and Hsp16 are able to bind to different lipids isolated from S. pombe, whose interaction might provide a powerful protection against heat-induced damages of the membranes. Our data suggest that all the three investigated thermoprotectant macromolecules play a pivotal role during the thermal stress management in the fission yeast.

Induction and phosphorylation of the small heat shock proteins HspB1/Hsp25 and HspB5/αB-crystallin in the rat retina upon optic nerve injury

Several eye diseases are associated with axonal injury in the optic nerve, which normally leads to degeneration of retinal ganglion cells (RGCs) and subsequently to loss of vision. There is experimental evidence that some members of the small heat shock protein family (HspBs) are upregulated upon optic nerve injury (ONI) in the retina and sufficient to promote RGC survival. These data raise the question as to whether other family members may play a similar role in this context. Here, we performed a comprehensive comparative study comprising all HspBs in an experimental model of ONI. We found that five HspBs were expressed in the adult rat retina at control conditions but only HspB1 and HspB5 were upregulated in response to ONI. Furthermore, HspB1 and HspB5 were constitutively phosphorylated in Müller cells at serine 15 and serine 59, respectively. In RGCs, phosphorylation was stimulated by ONI and occurred at serine 86 of HspB1 and at serine 19 and 45 of HspB5. These data suggest that of all small heat shock proteins, only HspB1 and HspB5 might be of protective value for RGCs after ONI and that this process might be regulated by phosphorylation at serine 86 of HspB1 and serine 19 and serine 45 of HspB5. The molecular targets of phosphoHspB1 and phosphoHspB5 remain to be identified.

Small heat shock proteins are induced during multiple sclerosis lesion development in white but not grey matter

Introduction

The important protective role of small heat-shock proteins (HSPs) in regulating cellular survival and migration, counteracting protein aggregation, preventing apoptosis, and regulating inflammation in the central nervous system is now well-recognized. Yet, their role in the neuroinflammatory disorder multiple sclerosis (MS) is largely undocumented. With the exception of alpha B-crystallin (HSPB5), little is known about the roles of small HSPs in disease.

Results

Here, we examined the expression of four small HSPs during lesion development in MS, focussing on their cellular distribution, and regional differences between white matter (WM) and grey matter (GM). It is well known that MS lesions in these areas differ markedly in their pathology, with substantially more intense blood-brain barrier damage, leukocyte infiltration and microglial activation typifying WM but not GM lesions.

We analysed transcript levels and protein distribution profiles for HSPB1, HSPB6, HSPB8 and HSPB11 in MS lesions at different stages, comparing them with normal-appearing brain tissue from MS patients and non-neurological controls. During active stages of demyelination in WM, and especially the centre of chronic active MS lesions, we found significantly increased expression of HSPB1, HSPB6 and HSPB8, but not HSPB11. When induced, small HSPs were exclusively found in astrocytes but not in oligodendrocytes, microglia or neurons. Surprisingly, while the numbers of astrocytes displaying high expression of small HSPs were markedly increased in actively demyelinating lesions in WM, no such induction was observed in GM lesions. This difference was particularly obvious in leukocortical lesions covering both WM and GM areas.

Conclusions

Since induction of small HSPs in astrocytes is apparently a secondary response to damage, their differential expression between WM and GM likely reflects differences in mediators that accompany demyelination in either WM or GM during MS. Our findings also suggest that during MS, cortical structures fail to benefit from the protective actions of small HSPs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-015-0267-2) contains supplementary material, which is available to authorized users.

Association between small heat shock protein B11 and the prognostic value of MGMT promoter methylation in patients with high-grade glioma

OBJECT This study investigated the role and prognostic value of heat shock proteins (HSPs) in glioma. METHODS Data from 3 large databases of glioma samples (Chinese Glioma Genome Atlas, Repository for Molecular Brain Neoplasia Data, and GSE16011), which contained whole-genome messenger RNA microarray expression data and patients' clinical data, were analyzed. Immunohistochemical analysis was performed to validate protein expression in another set of 50 glioma specimens. RESULTS Of 28 HSPs, 11 were overexpressed in high-grade glioma (HGG) compared with low-grade glioma. A univariate Cox analysis revealed that HSPB11 has significant prognostic value for each glioma grade, which was validated by a Kaplan-Meier survival analysis. HSPB11 expression was associated with poor prognosis and was independently correlated with overall survival (OS) in HGG. This study further explored the combined role of HSPB11 and other molecular markers in HGG, such as isocitrate dehydrogenase 1 (IDH1) mutation and O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status. HSPB11 expression was able to refine the prognostic value of IDH1 mutation in patients with HGG. However, when combined with MGMT promoter methylation status, among patients with a methylated MGMT promoter, those with lower levels of HSPB11 expression had longer OS and progression-free survival than patients with higher levels of HSPB11 expression or with an unmethylated MGMT promoter. Moreover, within the MGMT promoter methylation group, patients with low levels of HSPB11 expression were more sensitive to combined radiochemotherapy than those with high levels of HSPB11 expression, which may explain why some patients with HGG with a methylated MGMT promoter show tolerance to radiochemotherapy. CONCLUSIONS HSPB11 was identified as a novel prognostic marker in patients with HGG. Together with MGMT promoter methylation status, HSPB11 expression can predict outcome for patients with HGG and identify those who would most benefit from combined radiochemotherapy.

Reaction of small heat-shock proteins to different kinds of cellular stress in cultured rat hippocampal neurons

Upregulation of small heat-shock proteins (sHsps) in response to cellular stress is one mechanism to increase cell viability.We previously described that cultured rat hippocampal neurons express five of the 11 family members but only upregulate two of them (HspB1 and HspB5) at the protein level after heat stress. Since neurons have to cope with many other pathological conditions, we investigated in this study the expression of all five expressed sHsps on mRNA and protein level after sublethal sodium arsenite and oxidative and hyperosmotic stress. Under all three conditions, HspB1, HspB5, HspB6, and HspB8 but not HspB11 were consistently upregulated but showed differences in the time course of upregulation. The increase of sHsps always occurred earlier on mRNA level compared with protein levels. We conclude from our data that these four upregulated sHsps (HspB1, HspB5, HspB6, HspB8) act together in different proportions in the protection of neurons from various stress conditions.

Pathology-dependent effects linked to small heat shock proteins expression: an update

Small heat shock proteins (small Hsps) are stress-induced molecular chaperones that act as holdases towards polypeptides that have lost their folding in stress conditions or consequently of mutations in their coding sequence. A cellular protection against the deleterious effects mediated by damaged proteins is thus provided to cells. These chaperones are also highly expressed in response to protein conformational and inflammatory diseases and cancer pathologies. Through specific and reversible modifications in their phospho-oligomeric organization, small Hsps can chaperone appropriate client proteins in order to provide cells with resistance to different types of injuries or pathological conditions. By helping cells to better cope with their pathological status, their expression can be either beneficial, such as in diseases characterized by pathological cell degeneration, or deleterious when they are required for tumor cell survival. Moreover, small Hsps are actively released by cells and can act as immunogenic molecules that have dual effects depending on the pathology. The cellular consequences linked to their expression levels and relationships with other Hsps as well as therapeutic strategies are discussed in view of their dynamic structural organization required to interact with specific client polypeptides.

Heat shock proteins and heat shock factor 1 in carcinogenesis and tumor development: an update

Heat shock proteins (HSP) are a subset of the molecular chaperones, best known for their rapid and abundant induction by stress. HSP genes are activated at the transcriptional level by heat shock transcription factor 1 (HSF1). During the progression of many types of cancer, this heat shock transcriptional regulon becomes co-opted by mechanisms that are currently unclear, although evidently triggered in the emerging tumor cell. Concerted activation of HSF1 and the accumulation of HSPs then participate in many of the traits that permit the malignant phenotype. Thus, cancers of many histologies exhibit activated HSF1 and increased HSP levels that may help to deter tumor suppression and evade therapy in the clinic. We review here the extensive work that has been carried out and is still in progress aimed at (1) understanding the oncogenic mechanisms by which HSP genes are switched on, (2) determining the roles of HSF1/HSP in malignant transformation and (3) discovering approaches to therapy based on disrupting the influence of the HSF1-controlled transcriptome in cancer.

IFT25 links the signal-dependent movement of Hedgehog components to intraflagellar transport

The intraflagellar transport (IFT) system is required for building primary cilia, sensory organelles that cells use to respond to their environment. IFT particles are composed of about 20 proteins, and these proteins are highly conserved across ciliated species. IFT25, however, is absent from some ciliated organisms, suggesting that it may have a unique role distinct from ciliogenesis. Here, we generate an Ift25 null mouse and show that IFT25 is not required for ciliary assembly but is required for proper Hedgehog signaling, which in mammals occurs within cilia. Mutant mice die at birth with multiple phenotypes, indicative of Hedgehog signaling dysfunction. Cilia lacking IFT25 have defects in the signal-dependent transport of multiple Hedgehog components including Patched-1, Smoothened, and Gli2, and fail to activate the pathway upon stimulation. Thus, IFT function is not restricted to building cilia where signaling occurs, but also plays a separable role in signal transduction events.

Crystal structure of the intraflagellar transport complex 25/27

The cilium is an important organelle that is found on many eukaryotic cells, where it serves essential functions in motility, sensory reception and signalling. Intraflagellar transport (IFT) is a vital process for the formation and maintenance of cilia. We have determined the crystal structure of Chlamydomonas reinhardtii IFT25/27, an IFT sub-complex, at 2.6 Å resolution. IFT25 and IFT27 interact via a conserved interface that we verify biochemically using structure-guided mutagenesis. IFT27 displays the fold of Rab-like small guanosine triphosphate hydrolases (GTPases), binds GTP and GDP with micromolar affinity and has very low intrinsic GTPase activity, suggesting that it likely requires a GTPase-activating protein (GAP) for robust GTP turnover. A patch of conserved surface residues contributed by both IFT25 and IFT27 is found adjacent to the GTP-binding site and could mediate the binding to other IFT proteins as well as to a potential GAP. These results provide the first step towards a high-resolution structural understanding of the IFT complex.

Structure-functions of HspB1 (Hsp27)

Human HspB1 (also denoted Hsp27) is a well-known member, together with alphaB-crystallin, of the small heat-shock (or stress) proteins (sHsps) (20-40 kDa). In this chapter, I describe procedures for testing the oligomeric and phosphorylation patterns of HspB1 as well as its interaction with specific partner/client polypeptides using tissue culture cells genetically modified to express different levels of this protein. The procedures have been developed in my laboratory and could be used in any well-established cellular laboratory. In addition, the different procedures presented here could be extended to test the nine other human sHsp members as well as sHsps from other species.

Truncation attenuates molecular chaperoning and apoptosis inhibition by p26, a small heat shock protein from Artemia franciscana

The small heat shock proteins (sHSPs), which prevent irreversible protein denaturation and inhibit apoptosis, consist of an amino-terminus, the canonical α-crystallin domain, and a carboxy-terminal extension. It remains difficult, however, to define sHSP structure-function relationships and with this in mind p26, an sHSP from the crustacean Artemia franciscana, was truncated by deletion mutagenesis. Wild-type p26 cDNA and three truncated variants inserted into the eukaryotic expression vector pcDNA3.1/HisC were used to generate stably transfected 293H cells. p26 shielded transfected cells against death upon exposure to heat and oxidative stress. Truncation reduced chaperone activity, with cells synthesizing the p26 α-crystallin domain being the least resistant. Wild-type p26 inhibited apoptosis in transfected cells, with protection against oxidation-generated apoptosis being more effective than that against heat-induced apoptosis. Truncation reduced p26 apoptotic inhibitory activity, with the α-crystallin domain again being the least effective. The results show that a crustacean sHSP functions effectively in mammalian cells, demonstrating interchangeability of these proteins between distantly related organisms and indicating similarities in their mechanisms of action. Moreover, maximal activity was observed for full-length p26, indicating that structural elements required for chaperone activity and apoptosis inhibition reside throughout the protein.

Why proteins without an alpha-crystallin domain should not be included in the human small heat shock protein family HSPB

The presence of an alpha-crystallin domain documents the evolutionary relatedness of the ubiquitous family of small heat shock proteins. Sequence and three-dimensional structure provide no evidence for the presence of such a domain in HSPC034, recently proposed as the 11th member of the human HSPB family. Also, phylogenetic analyses detect no relationship between HSPC034 and the human HSPB1-10 sequences. Arguments are provided as to why inclusion in the HSPB family of proteins like HSPC034, which resemble small heat shock proteins in being heat-inducible and having chaperone-like properties and a low monomeric mass, but are evolutionarily unrelated, is misleading and confusing.

HA-tagging of putative flagellar proteins in Chlamydomonas reinhardtii identifies a novel protein of intraflagellar transport complex B

Proteomic analysis of flagella from the green alga Chlamydomonas reinhardtii has identified over 600 putative flagellar proteins. The genes encoding nine of these not previously characterized plus the previously described PACRG protein were cloned, inserted into a vector adding a triple-HA tag to the C-terminus of the gene product, and transformed into C. reinhardtii. Expression was confirmed by western blotting. Indirect immunofluorescence located all 10 fusion proteins in the flagellum; PACRG was localized to a subset of outer doublet microtubules. For some proteins, additional signal was observed in the cell body. Among the latter was FAP232-HA, which showed a spotted distribution along the flagella and an accumulation at the basal bodies. This pattern is characteristic for intraflagellar transport (IFT) proteins. FAP232-HA co-localized with the IFT protein IFT46 and co-sedimented with IFT particles in sucrose gradients. Furthermore, it co-immunoprecipitated with IFT complex B protein IFT46, but not with IFT complex A protein IFT139. We conclude that FAP232 is a novel component of IFT complex B and rename it IFT25. Homologues of IFT25 are encoded in the genomes of a subset of organisms that assemble cilia or flagella; C. reinhardtii IFT25 is 37% identical to the corresponding human protein. Genes encoding IFT25 homologues are absent from the genomes of organisms that lack cilia and flagella and, interestingly, also from those of Drosophila melanogaster and Caenorhabditis elegans, suggesting that IFT25 has a specialized role in IFT that is not required for the assembly of cilia or flagella in the worm and fly. Cell Motil. Cytoskeleton 2009. (c) 2009 Wiley-Liss, Inc.

Characterization of mouse IFT complex B

The primary cilium plays a key role in the development of mammals and in the maintenance of health. Primary cilia are assembled and maintained by the process of intraflagellar transport (IFT). In this work, we characterize mouse IFT complex B by identifying all of the mammalian orthologues of complex B and B-associated proteins previously identified in Chlamydomonas and Caenorhabditis and also identify a new component (IFT25/Hspb11) of complex B by database analysis. We tagged each of these proteins with the FLAG epitope and show that all except IFT172 and IFT20 localize to cilia and the peri-basal body or centrosomal region at the base of cilia. All of the proteins except IFT172 immunoprecipitate IFT88 indicating that they are co-assembled into a complex. IFT20 is the only complex B protein that localizes to the Golgi apparatus. However, overexpression of IFT54/Traf3ip1, the mouse orthologue of Dyf-11/Elipsa, displaces IFT20 from the Golgi apparatus. IFT54 does not localize to the Golgi complex nor does it interact with GMAP210, which is the protein that anchors IFT20 to the Golgi apparatus. This suggests that IFT54s effect on IFT20 is a dominant negative phenotype caused by its overexpression. Cell Motil. Cytoskeleton 2009. (c) 2009 Wiley-Liss, Inc.

Structural and functional diversity in the family of small heat shock proteins from the parasite Toxoplasma gondii

Small heat shock proteins (sHsps) are ubiquitous molecular chaperones which prevent the nonspecific aggregation of non-native proteins. Five potential sHsps exist in the parasite Toxoplasma gondii. They are located in different intracellular compartments including mitochondria and are differentially expressed during the parasite's life cycle. Here, we analyzed the structural and functional properties of all five proteins. Interestingly, this first in vitro characterization of sHsps from protists showed that all T. gondii sHsps exhibit the characteristic properties of sHsps such as oligomeric structure and chaperone activity. However, differences in their quaternary structure and in their specific chaperone properties exist. On the structural level, the T. gondii sHsps can be divided in small (12-18 subunits) and large (24-32 subunits) oligomers. Furthermore, they differ in their interaction with non-native proteins. While some bind substrates tightly, others interact more transiently. The chaperone activity of the three more mono-disperse T. gondii sHsps is regulated by temperature with a decrease in temperature leading to the activation of chaperone activity, suggesting an adaption to specific steps of the parasite's life cycle.

HSPB7 is a SC35 speckle resident small heat shock protein

BACKGROUND

The HSPB family is one of the more diverse families within the group of HSP families. Some members have chaperone-like activities and/or play a role in cytoskeletal stabilization. Some members also show a dynamic, stress-induced translocation to SC35 splicing speckles. If and how these features are interrelated and if they are shared by all members are yet unknown.

METHODS

Tissue expression data and interaction and co-regulated gene expression data of the human HSPB members was analyzed using bioinformatics. Using a gene expression library, sub-cellular distribution of the diverse members was analyzed by confocal microscopy. Chaperone activity was measured using a cellular luciferase refolding assay.

RESULTS

Online databases did not accurately predict the sub-cellular distribution of all the HSPB members. A novel and non-predicted finding was that HSPB7 constitutively localized to SC35 splicing speckles, driven by its N-terminus. Unlike HSPB1 and HSPB5, that chaperoned heat unfolded substrates and kept them folding competent, HSPB7 did not support refolding.

CONCLUSION

Our data suggest a non-chaperone-like role of HSPB7 at SC35 speckles.

GENERAL SIGNIFICANCE

The functional divergence between HSPB members seems larger than previously expected and also includes non-canonical members lacking classical chaperone-like functions.

Correlation between the progressive cytoplasmic expression of a novel small heat shock protein (Hsp16.2) and malignancy in brain tumors

Background

Small heat shock proteins are molecular chaperones that protect proteins against stress-induced aggregation. They have also been found to have anti-apoptotic activity and to play a part in the development of tumors. Recently, we identified a new small heat shock protein, Hsp16.2 which displayed increased expression in neuroectodermal tumors. Our aim was to investigate the expression of Hsp16.2 in different types of brain tumors and to correlate its expression with the histological grade of the tumor.

Methods

Immunohistochemistry with a polyclonal antibody to Hsp16.2 was carried out on formalin-fixed, paraffin-wax-embedded sections using the streptavidin-biotin method. 91 samples were examined and their histological grade was defined. According to the intensity of Hsp16.2 immunoreactivity, low (+), moderate (++), high (+++) or none (-) scores were given.

Immunoblotting was carried out on 30 samples of brain tumors using SDS-polyacrylamide gel electrophoresis and Western-blotting.

Results

Low grade (grades 1–2) brain tumors displayed low cytoplasmic Hsp16.2 immunoreactivity, grade 3 tumors showed moderate cytoplasmic staining, while high grade (grade 4) tumors exhibited intensive cytoplasmic Hsp16.2 staining. Immunoblotting supported the above mentioned results. Normal brain tissue acted as a negative control for the experiment, since the cytoplasm did not stain for Hsp16.2. There was a positive correlation between the level of Hsp16.2 expression and the level of anaplasia in different malignant tissue samples.

Conclusion

Hsp16.2 expression was directly correlated with the histological grade of brain tumors, therefore Hsp16.2 may have relevance as becoming a possible tumor marker.

Differentially expressed proteins in cerulein-stimulated pancreatic acinar cells: implication for acute pancreatitis

The proteins expressed in pancreatic acinar cells during the initiation of acute pancreatitis may determine the severity of the disease. Cerulein pancreatitis is one of the best characterized models for acute pancreatitis. Present study aims to determine the differentially expressed proteins in cerulein-stimulated pancreatic acinar cells as an in vitro model for acute pancreatitis. Rat pancreatic acinar AR42J cells were treated with 10(-8)M cerulein for 12h. The protein patterns separated by two-dimensional electrophoresis using pH gradients of 5-8 were compared between the cells treated without cerulein and those with cerulein. The changed proteins were conclusively identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of the peptide digests. As a result, 10 proteins (Orp150 protein, protein disulfide isomerase related protein, dnaK-type molecular chaperone hsp72-ps1, mitochondrial glutamate dehydrogenase, similar to chaperonin containing TCP-1 beta subunit, RuvB-like protein 1, heterogeneous nuclear ribonucleoprotein H1, aldehyde reductase 1, triosephosphate isomerase 1, peroxiredoxin 2) were up-regulated while four proteins (vasolin-containing protein, 78 kDa glucose-regulated protein precursor, heat shock protein 8, adenosylhomocysteinase) were down-regulated by cerulein in pancreatic acinar AR42J cells. These proteins are related to chaperone, cell defense mechanism against oxidative stress or DNA damage, anti-apoptosis and energy generation. The differentially expressed proteins by ceruein share their functional roles in pancreatic acinar cells, suggesting the possible involvement of oxidative stress, DNA damage, and anti-apoptosis in pathogenesis of acute pancreatitis. Proteins involved in cellular defense mechanism and energy production may protect pancreatic acinar cells during the development of pancreatitis.