Stress granule-mediated RNA regulatory mechanism in Alzheimer's disease

Living organisms experience a range of stresses. To cope effectively with these stresses, eukaryotic cells have evolved a sophisticated mechanism involving the formation of stress granules (SGs), which play a crucial role in protecting various types of RNA species under stress, such as mRNAs and long non-coding RNAs (lncRNAs). SGs are non-membranous cytoplasmic ribonucleoprotein (RNP) granules, and the RNAs they contain are translationally stalled. Importantly, SGs have been thought to contribute to the pathophysiology of neurodegenerative diseases, including Alzheimer's disease (AD). SGs also contain multiple RNA-binding proteins (RBPs), several of which have been implicated in AD progression. SGs are transient structures that dissipate after stress relief. However, the chronic stresses associated with aging lead to the persistent formation of SGs and subsequently to solid-like pathological SGs, which could impair cellular RNA metabolism and also act as a nidus for the aberrant aggregation of AD-associated proteins. In this paper, we provide a comprehensive summary of the physical basis of SG-enriched RNAs and SG-resident RBPs. We then review the characteristics of AD-associated gene transcripts and their similarity to the SG-enriched RNAs. Furthermore, we summarize and discuss the functional implications of SGs in neuronal RNA metabolism and the aberrant aggregation of AD-associated proteins mediated by SG-resident RBPs in the context of AD pathogenesis. Geriatr Gerontol Int 2024; 24: 7-14.

Formation, function, and pathology of RNP granules

Ribonucleoprotein (RNP) granules are diverse membrane-less organelles that form through multivalent RNA-RNA, RNA-protein, and protein-protein interactions between RNPs. RNP granules are implicated in many aspects of RNA physiology, but in most cases their functions are poorly understood. RNP granules can be described through four key principles. First, RNP granules often arise because of the large size, high localized concentrations, and multivalent interactions of RNPs. Second, cells regulate RNP granule formation by multiple mechanisms including posttranslational modifications, protein chaperones, and RNA chaperones. Third, RNP granules impact cell physiology in multiple manners. Finally, dysregulation of RNP granules contributes to human diseases. Outstanding issues in the field remain, including determining the scale and molecular mechanisms of RNP granule function and how granule dysfunction contributes to human disease.

Stress Granules in Cancer

The capacity of cells to organize complex biochemical reactions in intracellular space is a fundamental organizational principle of life. Key to this organization is the compartmentalization of the cytoplasm into distinct organelles, which is frequently achieved through intracellular membranes. Recent evidence, however, has added a new layer of flexibility to cellular compartmentalization. As such, in response to specific stimuli, liquid-liquid phase separations can lead to the rapid rearrangements of the cytoplasm to form membraneless organelles. Stress granules (SGs) are one such type of organelle that form specifically when cells are faced with stress stimuli, to aid cells in coping with stress. Inherently, altered SG formation has been linked to the pathogenesis of diseases associated with stress and inflammatory conditions, including cancer. Exciting discoveries have indicated an intimate link between SGs and tumorigenesis. Several pro-tumorigenic signaling molecules including the RAS oncogene, mTOR, and histone deacetylase 6 (HDAC6) have been shown to upregulate SG formation. Based on these studies, SGs have emerged as structures that can integrate oncogenic signaling and tumor-associated stress stimuli to enhance cancer cell fitness. In addition, growing evidence over the past decade suggests that SGs function not only to regulate the switch between survival and cell death, but also contribute to cancer cell proliferation, invasion, metastasis, and drug resistance. Although much remains to be learned about the role of SGs in tumorigenesis, these studies highlight SGs as a key regulatory hub in cancer and a promising therapeutic target.

The Emerging Role of Stress Granules in Hepatocellular Carcinoma

Stress granules (SGs) are small membrane-free cytosolic liquid-phase ordered entities in which mRNAs are protected and translationally silenced during cellular adaptation to harmful conditions (e.g., hypoxia, oxidative stress). This function is achieved by structural and functional SG components such as scaffold proteins and RNA-binding proteins controlling the fate of mRNAs. Increasing evidence indicates that the capacity of cells to assemble/disassemble functional SGs may significantly impact the onset and the development of metabolic and inflammatory diseases, as well as cancers. In the liver, the abnormal expression of SG components and formation of SG occur with chronic liver diseases, hepatocellular carcinoma (HCC), and selective hepatic resistance to anti-cancer drugs. Although, the role of SG in these diseases is still debated, the modulation of SG assembly/disassembly or targeting the expression/activity of specific SG components may represent appealing strategies to treat hepatic disorders and potentially cancer. In this review, we discuss our current knowledge about pathophysiological functions of SGs in HCC as well as available molecular tools and drugs capable of modulating SG formation and functions for therapeutic purposes.

Reduced Granule Cell Proliferation and Molecular Dysregulation in the Cerebellum of Lysosomal Acid Phosphatase 2 (ACP2) Mutant Mice

Lysosomal acid phosphatase 2 (Acp2) mutant mice (naked-ataxia, nax) have a severe cerebellar cortex defect with a striking reduction in the number of granule cells. Using a combination of in vivo and in vitro immunohistochemistry, Western blotting, BrdU assays, and RT-qPCR, we show downregulation of MYCN and dysregulation of the SHH signaling pathway in the nax cerebellum. MYCN protein expression is significantly reduced at P10, but not at the peak of proliferation at around P6 when the number of granule cells is strikingly reduced in the nax cerebellum. Despite the significant role of the SHH-MycN pathway in granule cell proliferation, our study suggests that a broader molecular pathway and additional mechanisms regulating granule cell development during the clonal expansion period are impaired in the nax cerebellum. In particular, our results indicate that downregulation of the protein synthesis machinery may contribute to the reduced number of granule cells in the nax cerebellum.

Structural and functional polarisation of human pancreatic beta cells in islets from organ donors with and without type 2 diabetes

AIMS/HYPOTHESIS

We hypothesised that human beta cells are structurally and functional polarised with respect to the islet capillaries. We set out to test this using confocal microscopy to map the 3D spatial arrangement of key proteins and live-cell imaging to determine the distribution of insulin granule fusion around the cells.

METHODS

Human pancreas samples were rapidly fixed and processed using the pancreatic slice technique, which maintains islet structure and architecture. Slices were stained using immunofluorescence for polarity markers (scribble, discs large [Dlg] and partitioning defective 3 homologue [Par3]) and presynaptic markers (liprin, Rab3-interacting protein [RIM2] and piccolo) and imaged using 3D confocal microscopy. Isolated human islets were dispersed and cultured on laminin-511-coated coverslips. Live 3D two-photon microscopy was used on cultured cells to image exocytic granule fusion events upon glucose stimulation.

RESULTS

Assessment of the distribution of endocrine cells across human islets found that, despite distinct islet-to-islet complexity and variability, including multi-lobular islets, and intermixing of alpha and beta cells, there is still a striking enrichment of alpha cells at the islet mantle. Measures of cell position demonstrate that most beta cells contact islet capillaries. Subcellularly, beta cells consistently position polar determinants, such as Par3, Dlg and scribble, with a basal domain towards the capillaries and apical domain at the opposite face. The capillary interface/vascular face is enriched in presynaptic scaffold proteins, such as liprin, RIM2 and piccolo. Interestingly, enrichment of presynaptic scaffold proteins also occurs where the beta cells contact peri-islet capillaries, suggesting functional interactions. We also observed the same polarisation of synaptic scaffold proteins in islets from type 2 diabetic patients. Consistent with polarised function, isolated beta cells cultured onto laminin-coated coverslips target insulin granule fusion to the coverslip.

CONCLUSIONS/INTERPRETATION

Structural and functional polarisation is a defining feature of human pancreatic beta cells and plays an important role in the control of insulin secretion.

Spatiotemporal Proteomic Analysis of Stress Granule Disassembly Using APEX Reveals Regulation by SUMOylation and Links to ALS Pathogenesis

Stress granules (SGs) are cytoplasmic assemblies of proteins and non-translating mRNAs. Whereas much has been learned about SG formation, a major gap remains in understanding the compositional changes SGs undergo during normal disassembly and under disease conditions. Here, we address this gap by proteomic dissection of the SG temporal disassembly sequence using multi-bait APEX proximity proteomics. We discover 109 novel SG proteins and characterize distinct SG substructures. We reveal dozens of disassembly-engaged proteins (DEPs), some of which play functional roles in SG disassembly, including small ubiquitin-like modifier (SUMO) conjugating enzymes. We further demonstrate that SUMOylation regulates SG disassembly and SG formation. Parallel proteomics with amyotrophic lateral sclerosis (ALS)-associated C9ORF72 dipeptides uncovered attenuated DEP recruitment during SG disassembly and impaired SUMOylation. Accordingly, SUMO activity ameliorated C9ORF72-ALS-related neurodegeneration in Drosophila. By dissecting the SG spatiotemporal proteomic landscape, we provide an in-depth resource for future work on SG function and reveal basic and disease-relevant mechanisms of SG disassembly.

Unusual cerebrospinal fluid finding of intracytoplasmic granules in metaplastic carcinoma of the breast with acinar differentiation

Cerebrospinal fluid (CSF) evaluation for total and differential cell count is a common practice in pathology for evaluation of various disease conditions. Although rare, these CSF samples yield interesting and unusual morphological findings, which are not only of academic interest, but also may play key roles in diagnosis. For diagnosing metastatic carcinoma in brain and meninges, CSF examination is one of the important tools along with imaging studies. Metaplastic breast carcinoma (MBC) encompasses a rare (<1% of all breast cancers), aggressive and highly heterogeneous group of tumors. MBC is almost always estrogen receptor, progesterone receptor and Her2 negative (triple negative) and shows frequent early distant metastases as well as sub-optimal response to systemic therapies. The involvement of leptomeninges is most commonly associated with these triple- negative subtypes. In this report, we present an unusual case of malignant cells with prominent intracytoplasmic granules in CSF smears of a 46-year-old female with metastatic MBC with acinar differentiation. An extensive review of literature in English language did not return any other reports of a similar finding.

Novel manifestations of immune dysregulation and granule defects in gray platelet syndrome

Gray platelet syndrome (GPS) is a rare recessive disorder caused by biallelic variants in NBEAL2 and characterized by bleeding symptoms, the absence of platelet α-granules, splenomegaly, and bone marrow (BM) fibrosis. Due to the rarity of GPS, it has been difficult to fully understand the pathogenic processes that lead to these clinical sequelae. To discern the spectrum of pathologic features, we performed a detailed clinical genotypic and phenotypic study of 47 patients with GPS and identified 32 new etiologic variants in NBEAL2. The GPS patient cohort exhibited known phenotypes, including macrothrombocytopenia, BM fibrosis, megakaryocyte emperipolesis of neutrophils, splenomegaly, and elevated serum vitamin B12 levels. Novel clinical phenotypes were also observed, including reduced leukocyte counts and increased presence of autoimmune disease and positive autoantibodies. There were widespread differences in the transcriptome and proteome of GPS platelets, neutrophils, monocytes, and CD4 lymphocytes. Proteins less abundant in these cells were enriched for constituents of granules, supporting a role for Nbeal2 in the function of these organelles across a wide range of blood cells. Proteomic analysis of GPS plasma showed increased levels of proteins associated with inflammation and immune response. One-quarter of plasma proteins increased in GPS are known to be synthesized outside of hematopoietic cells, predominantly in the liver. In summary, our data show that, in addition to the well-described platelet defects in GPS, there are immune defects. The abnormal immune cells may be the drivers of systemic abnormalities such as autoimmune disease.

Stress Granule Formation Attenuates RACK1-Mediated Apoptotic Cell Death Induced by Morusin

Stress granules are membraneless organelles composed of numerous components including ribonucleoproteins. The stress granules are characterized by a dynamic complex assembly in response to various environmental stressors, which has been implicated in the coordinated regulation of diverse biological pathways, to exert a protective role against stress-induced cell death. Here, we show that stress granule formation is induced by morusin, a novel phytochemical displaying antitumor capacity through barely known mechanisms. Morusin-mediated induction of stress granules requires activation of protein kinase R (PKR) and subsequent eIF2α phosphorylation. Notably, genetic inactivation of stress granule formation mediated by G3BP1 knockout sensitized cancer cells to morusin treatment. This protective function against morusin-mediated cell death can be attributed at least in part to the sequestration of receptors for activated C kinase-1 (RACK1) within the stress granules, which reduces caspase-3 activation. Collectively, our study provides biochemical evidence for the role of stress granules in suppressing the antitumor capacity of morusin, proposing that morusin treatment, together with pharmacological inhibition of stress granules, could be an efficient strategy for targeting cancer.

Treatment of cancer cells with Lapatinib negatively regulates general translation and induces stress granules formation

Stress granules (SG) are cytoplasmic RNA granules that form during various types of stress known to inhibit general translation, including oxidative stress, hypoxia, endoplasmic reticulum stress (ER), ionizing radiations or viral infection. Induction of these SG promotes cell survival in part through sequestration of proapoptotic molecules, resulting in the inactivation of cell death pathways. SG also form in cancer cells, but studies investigating their formation upon treatment with chemotherapeutics are very limited. Here we identified Lapatinib (Tykerb / Tyverb®), a tyrosine kinase inhibitor used for the treatment of breast cancers as a new inducer of SG in breast cancer cells. Lapatinib-induced SG formation correlates with the inhibition of general translation initiation which involves the phosphorylation of the translation initiation factor eIF2α through the kinase PERK. Disrupting PERK-SG formation by PERK depletion experiments sensitizes resistant breast cancer cells to Lapatinib. This study further supports the assumption that treatment with anticancer drugs activates the SG pathway, which may constitute an intrinsic stress response used by cancer cells to resist treatment.

Biomolecular condensates in neurodegeneration and cancer

The intracellular environment is partitioned into functionally distinct compartments containing specific sets of molecules and reactions. Biomolecular condensates, also referred to as membrane-less organelles, are diverse and abundant cellular compartments that lack membranous enclosures. Molecules assemble into condensates by phase separation; multivalent weak interactions drive molecules to separate from their surroundings and concentrate in discrete locations. Biomolecular condensates exist in all eukaryotes and in some prokaryotes, and participate in various essential house-keeping, stress-response and cell type-specific processes. An increasing number of recent studies link abnormal condensate formation, composition and material properties to a number of disease states. In this review, we discuss current knowledge and models describing the regulation of condensates and how they become dysregulated in neurodegeneration and cancer. Further research on the regulation of biomolecular phase separation will help us to better understand their role in cell physiology and disease.

Psammaplysin F increases the efficacy of bortezomib and sorafenib through regulation of stress granule formation

The past few decades have delivered significant improvements in diagnosis and treatment of cancer, however, despite these improvements cancer continues to be a major global health issue requiring the urgent development of new strategies for treatment. Stress granules are cytoplasmic structures that triage gene expression in response to environmental stresses, including chemotherapies, and have been implicated in the development of drug resistance. One novel approach to developing a new anti-cancer strategy involves inhibiting stress granules with compounds derived from natural products. In a previous rapid screen, a subset of 132 compounds from the Davis Open Access Natural Product Library was screened using a stress granule inhibition assay and provisionally one hit was identified which was the known marine sponge-derived metabolite, psammaplysin F. Using cell based assays psammaplysin F was assessed to determine whether it could inhibit the formation of stress granules after exposure to sodium arsenite in Vero, HEK293 MCF7, T47D, HeLa and MCF7MDR cells by analysing the number of stress granules using high content imaging. A significant reduction in the number of stress granules was observed and subsequent analysis by western blot revealed that treatment with psammaplysin F decreased levels of phosphorylated eIF2α. Combinational studies in MCF7, HeLa and MCF7MDR cells revealed that psammaplysin F increased the efficacy of bortezomib and sorafenib and a synergistic effect was observed in vitro. Stress granules appear to be one tool in a battery of responses that cancer cells can exploit to elicit drug resistance. Disrupting stress granule formation by use of orally available drugs presents a potential mechanism to restore drug efficacy. The work presented here provides evidence that small molecules derived from nature, such as psammaplysin F, can prevent the formation of stress granules and therefore may represent a useful strategy to improving drug efficacy.

Evaluating Stress Granules in Pancreatic Cancer In Vitro and In Vivo

Stress granules are nonmembranous organelles that function as a stress-adaptation mechanism. We have recently shown that stress granules are mobilized by mutant KRAS pancreatic cancer cells under stress to enhance tumor fitness and survival. In this chapter, we outline a method for inducing, detecting, and quantifying stress granules in pancreatic cancer cells in vitro and in vivo. This method can be utilized to better understand the mechanisms driving stress granule formation and their role in pancreatic tumorigenesis.

Preterm birth disrupts cerebellar development by affecting granule cell proliferation program and Bergmann glia

Preterm birth is a leading cause of long-term motor and cognitive deficits. Clinical studies suggest that some of these deficits result from disruption of cerebellar development, but the mechanisms that mediate cerebellar abnormalities in preterm infants are largely unknown. Furthermore, it remains unclear whether preterm birth and precocious exposure to the ex-utero environment directly disrupt cerebellar development or indirectly by increasing the probability of cerebellar injury, including that resulting from clinical interventions and protocols associated with the care of preterm infants. In this study, we analyzed the cerebellum of preterm pigs delivered via c-section at 91% term and raised for 10 days, until term-equivalent age. The pigs did not receive any treatments known or suspected to affect cerebellar development and had no evidence of brain damage. Term pigs sacrificed at birth were used as controls. Immunohistochemical analysis revealed that preterm birth did not affect either size or numbers of Purkinje cells or molecular layer interneurons at term-equivalent age. The number of granule cell precursors and Bergmann glial fibers, however, were reduced in preterm pigs. Preterm pigs had reduced proliferation but not differentiation of granule cells. qRT-PCR analysis of laser capture microdissected external granule cell layer showed that preterm pigs had a reduced expression of Ccnd1 (Cyclin D1), Ccnb1 (Cyclin B1), granule cell master regulatory transcription factor Atoh1, and signaling molecule Jag1. In vitro rescue experiments identified Jag1 as a central granule cell gene affected by preterm birth. Thus, preterm birth and precocious exposure to the ex-utero environment disrupt cerebellum by modulating expression of key cerebellar developmental genes, predominantly affecting development of granule precursors and Bergmann glia.

Progressive accumulation of autofluorescent granules in macrophages in rat striatum after systemic 3-nitropropionic acid: a correlative light- and electron-microscopic study

A variety of tissue biomolecules and intracellular structures are known to be autofluorescent. However, autofluorescent signals in brain tissues often confound analysis of the fluorescent markers used for immunohistochemistry. While investigating tissue and cellular pathologies induced by 3-nitropropionic acid, a mitochondrial toxin selective for striatal neurons, we encountered many autofluorescent signals confined to the lesion core. These structures were excited by blue (wavelength = 488 nm) and yellow-orange (555 nm), but not by red (639 nm) or violet (405 nm) lasers, indicating that this autofluorescence overlaps with the emission spectra of commonly used fluorophores. Almost all of the autofluorescence was localized in activated microglia/macrophages, while reactive astrocytes emitted no detectable autofluorescence. Amoeboid brain macrophages filled with autofluorescent granules revealed very weak expression of the microglial marker, ionized calcium-binding adaptor molecule 1 (Iba1), while activated microglia with evident processes and intense Iba1 immunoreactivity contained scant autofluorescent granules. In addition, immunolabeling with two lysosomal markers, ED1/CD68 and lysosomal-associated membrane protein 1, showed a pattern complementary with autofluorescent signals in activated microglia/macrophages, implying that the autofluorescent structures reside within cytoplasm free of intact lysosomes. A correlative light- and electron-microscopic approach finally revealed the ultrastructural identity of the fluorescent granules, most of which matched to clusters of lipofuscin-like inclusions with varying morphology. Thus, autofluorescence in the damaged brain may reflect the presence of lipofuscin-laden brain macrophages, which should be taken into account when verifying any fluorescent signals that are likely to be correlated with activated microglia/macrophages after brain insults.

Cytoplasmic stress granules: Dynamic modulators of cell signaling and disease

Stress granule (SG) assembly is a conserved cellular strategy to minimize stress-related damage and promote cell survival. Beyond their fundamental role in the stress response, SGs have emerged as key players for human health. As such, SG assembly is associated with cancer, neurodegenerative disorders, ischemia, and virus infections. SGs and granule-related signaling circuits are therefore promising targets to improve therapeutic intervention for several diseases. This is clinically relevant, because pharmacological drugs can affect treatment outcome by modulating SG formation. As membraneless and highly dynamic compartments, SGs regulate translation, ribostasis and proteostasis. Moreover, they serve as signaling hubs that determine cell viability and stress recovery. Various compounds can modulate SG formation and dynamics. Rewiring cell signaling through SG manipulation thus represents a new strategy to control cell fate under various physiological and pathological conditions.

Clinical significance of granule-containing myeloma cells in patients with newly diagnosed multiple myeloma

The clinical features and prognostic significance of myeloma cells containing granules remain unclear. The purpose of this retrospective study was to investigate the clinical significance of granule-containing myeloma cells in patients with newly diagnosed multiple myeloma (NDMM). We retrospectively analyzed the records of 122 patients diagnosed with NDMM between January 2007 and December 2013. Granule-containing myeloma cells were defined as myeloma cells that exhibited three or more granules in their cytoplasm by May-Giemsa staining. The patients were classified into two groups, the granule-containing myeloma (GM) and nongranule-containing myeloma (non-GM) groups, depending on the proportion of myeloma cells that contained granules (cut-off value: 10%). There were 25 (20.5%) patients in the GM group. Patients in the GM group displayed significantly higher CD56 and CD49e expression than those in the non-GM group (t-test, P = 0.027 and 0.042). None of the patient characteristics differed significantly between the two groups. There was no significant difference in the chemotherapy profiles of the two groups, and the overall response rates of the two groups were similar. During the median follow-up period of 33.9 months, the overall survival (OS) in the GM group was similar to that in the non-GM group; 4-year OS of the GM and non-GM groups were 78.5% and 51.9%, respectively (P = 0.126). We concluded that cases of NDMM involving granule-containing myeloma cells are not infrequent. Moreover, CD56 and CD49e expression was significantly higher in the presence of myeloma cell populations, and the presence of granules did not affect survival.

Spontaneous Eosinophilic Granulated Round Cell Tumors in Rats

Morphologic and histochemical characteristics were noted for three spontaneous tumors with eosinophilic cytoplasmic granules that occurred in aged Fischer 344 rats. Macroscopic lesions were widely distributed in the body, mainly involving the intra-abdominal adipose tissue, pancreas, and mesenterium. These lesions were generally hard swellings with nodular and sclerosing areas. Bloody ascites was a concomitant finding. Histologically, the tumor cells were round, from 9 to 30 μm in diameter with one or two round to oval nuclei, and characterized by eosinophilic granules (0.5–2.0 μm) that stained definitely to weakly positive with the periodic acid-Schiff reaction and demonstrated no metachromasia with toluidine blue stain. Furthermore, the granules were characterized by a positive reaction with lectin histochemistry for concanavalin A (Con A), wheat germ agglutinin (WGA), phaseolus vulgaris agglutinin (PHA-E4), lens culinaris agglutinin (LCA), and recinus communis agglutinin (RCA-I) in all tumors and for ulex europaeus agglutinin (UEA-I), peanut agglutinin (PNA), and soybean agglutinin (SBA) in one tumor. Positive reactions for anti-rat mast cell protease II and CD8 were not demonstrated immunohistochemically. Abundant glycogen was noted in the large tumor cells from one rat. With electron microscopy, the cytoplasmic granules were identified as electron-dense homogenous bodies bounded by a single unit membrane. These characteristics are similar to those of granulated metrial gland cells, but further study is needed to clarify the cell of origin for these tumors.

[Age-related peculiarities of mast cell distribution in human esophagus wall]

Mast cells (MCs) were studied quantitatively and qualitatively in the wall of the esophagus (upper, middle and lower portions) of the individuals in the I period of mature age (22-35 years, n = 6) as well as in old and senile persons (61-82 years, n = 10). In all the individuals, the total number of MCs was found to increase from the upper portion of the esophagus towards the lower one. Within the esophageal wall, the total number of MCs decreased in the direction from tunica mucosa towards adventitia. During I period of mature age, the resting MCs filled with granules predominated, while the degranulating MCs were located in the lower esophageal segment. In the individuals of old and senile age, the degranulating MCs were more frequently observed in the upper and lower esophageal segments.

[MORPHOLOGICAL FEATURES OF NEUTROPHILS AND EOSINOPHILS GRANULES IN SAPPHIRE MINKS]

It has been established that sapphire minks have abnormality of subcellular structure of blood and bone marrow neutrophils and eosinophils. The abnormality consists in forming of abnormal "giant" granules. The si- ze and the number of abnormal granules significantly change during maturation of leucocytes in bone marrow. We have found differences between abnormal granules forming in neutrophils and eosinophils that depend on the maturing stage and the cells life cycle duration as well as morphofunctional features of these granulocytes.

Autophagy meets fused in sarcoma-positive stress granules

Mutations in fused in sarcoma and/or translocated in liposarcoma (FUS, TLS or FUS) are linked to familial cases of amyotrophic lateral sclerosis (ALS). Mutant FUS selectively accumulates into discrete cytosolic structures known as stress granules under various stress conditions. In addition, mutant FUS expression can alter the dynamics and morphology of stress granules. Although the link between mutant FUS and stress granules is well established, the mechanisms modulating stress granule formation and disassembly in the context of ALS are poorly understood. In this issue of Neurobiology of Aging, Ryu et al. uncover the impact of autophagy on the potential toxicity of mutant FUS-positive stress granules. The authors provide evidence indicating that enhanced autophagy activity reduces the number of stress granules, which in the case of cells containing mutant FUS-positive stress granules, is neuroprotective. Overall, this study identifies an intersection between the proteostasis network and alterations in RNA metabolism in ALS through the dynamic assembly and disassembly of stress granules.

Physiological protein aggregation run amuck: stress granules and the genesis of neurodegenerative disease

Recent advances in neurodegenerative diseases point to novel mechanisms of protein aggregation. RNA binding proteins are abundant in the nucleus, where they carry out processes such as RNA splicing. Neurons also express RNA binding proteins in the cytoplasm and processes to enable functions such as mRNA transport and local protein synthesis. The biology of RNA binding proteins turns out to have important features that appear to promote the pathophysiology of amyotrophic lateral sclerosis and might contribute to other neurodegenerative disease. RNA binding proteins consolidate transcripts to form complexes, termed RNA granules, through a process of physiological aggregation mediated by glycine rich domains that exhibit low protein complexity and in some cases share homology to similar domains in known prion proteins. Under conditions of cell stress these RNA granules expand, leading to form stress granules, which function in part to sequester specialized transcript and promote translation of protective proteins. Studies in humans show that pathological aggregates occurring in ALS, Alzheimer's disease, and other dementias co-localize with stress granules. One increasingly appealing hypothesis is that mutations in RNA binding proteins or prolonged periods of stress cause formation of very stable, pathological stress granules. The consolidation of RNA binding proteins away from the nucleus and neuronal arbors into pathological stress granules might impair the normal physiological activities of these RNA binding proteins causing the neurodegeneration associated with these diseases. Conversely, therapeutic strategies focusing on reducing formation of pathological stress granules might be neuroprotective.

Molecular and functional properties of densely and sparsely granulated GH-producing pituitary adenomas

OBJECTIVE

GH-producing pituitary adenomas display two distinct morphological patterns of cytoplasmic GH-containing secretory granules, namely the densely and sparsely granulated somatotroph adenoma subtype. It is unknown whether these morphological variants reflect distinct pathophysiological entities at the molecular level.

METHODS

In 28 GH-producing adenoma tissues from a consecutive set of patients undergoing pituitary surgery for acromegaly, we studied the GH granulation pattern, the expression of somatostatin receptor subtypes (SSTR) as well as the calcium, cAMP and ZAC1 pathways in primary adenoma cell cultures.

RESULTS

The expression of GSP oncogene was similar between densely and sparsely granulated somatotroph adenoma cells. There were no differences in the calcium, cAMP and ZAC1 pathways as well as in their regulation by SSTR agonists. SSTR2 was exclusively expressed in densely but not in sparsely granulated tumours (membrane expression 86 vs 0%; cytoplasmic expression 67 vs 0%). By contrast, expression of SSTR5 was only found in sparsely but not in densely granulated somatotroph adenomas (membrane expression 29 vs 0%; cytoplasmic expression 57 vs 0%).

CONCLUSIONS

Our results indicate that different granulation patterns in GH-producing adenomas do not reflect differences in pathways and factors pivotal for somatotroph differentiation and function. In vitro, the vast majority of both densely and sparsely granulated tumour cells were responsive to SSTR activation at the molecular level. Sparsely granulated adenomas lacking SSTR2, but expressing SSTR5, might be responsive to novel SSTR agonists with increased affinity to SSTR5.

Balancing the fat: lipid droplets and human disease

Lipid droplets (LDs) are dynamic, cytosolic lipid-storage organelles found in nearly all cell types. Too many or too few LDs during excess or deficient fat storage lead to many different human diseases. Recent insights into LD biology and LD protein functions shed new light on mechanisms underlying those metabolic pathologies. These findings will likely provide opportunities for treatment of diseases associated with too much or too little fat.

Malacoplakia of the seminal vesicles. Case report and particularities

OBJECTIVE

Malacoplakia is a rare chronic granulomatous disorder that mostly affects the urogenital system. This article describes a case of uncommon location of this disease at the level of the seminal vesicles and the clinical, imaging and histological particularities of this medical entity.

METHOD

We report the case of a 69 year-old male consulting for constitutional syndrome that presented a pelvic tumor on the image studies, possibly arising in the seminal vesicles.

RESULTS

The diagnosis was made after performing transrectal ultrasound and seminal vesicles biopsy by the pathognomonic histological findings of Michaelis Gutmann bodies. The presence of E. Coli in urine culture in our patient justified the use of a long-term antibiotic therapy such as quinolones with very good results.

CONCLUSION

Malacoplakia of the seminal vesicles is an extremely rare condition, sometimes with non-specific clinical presentation. Its diagnosis is histological and it has good response to prolonged antibiotic therapy with a benign outcome.

Digital clubbing as an unusual complication of the secondary hyperparathyroidism associated with atypical neutrophils: a case report

Digital clubbing is a rare clinical finding and usually represents a sign of underlying disease.There are only few cases of digital clubbing in patients with primary hyperparathyroidism or with secondary hyperparathyroidism (SHPT) during long-term hemodialysis. We haven't come across papers dealing with the relation of digital clubbing and SHPT caused by vitamin D deficiency. In this article, we report a case of 43 year-old female patient with prominent clubbing of the fingers and toes, and 22 year history of SHPT caused by vitamin D deficiency. Current radiographic findings of the hands and feet are actually uncommon, and they show massive osteolytic lesions of numerous phalanges, which is the consequence of long-time untreated SHPT. Besides, our patient has a rare case of neutrophils with bilobed nuclei and decreased cytoplasmic granularity. This paper for the first time describes digital clubbing as an unusual complication of the SHPT caused by vitamin D deficiency associated with atypical neutrophils.

Aberrant neurogenesis after stroke: a retroviral cell labeling study

BACKGROUND AND PURPOSE

Adult neurogenesis in the dentate gyrus is a unique form of brain plasticity that is strongly stimulated after stroke. We investigate the morphological properties of new granule cells, which are born and develop after the ischemic insult, and query whether these adult-born neurons properly integrate into the pre-existing hippocampal circuitries.

METHODS

Two well-established models were used to induce either small cortical infarcts (photothrombosis model) or large territorial infarcts (transient middle cerebral artery occlusion model). New granule cells were labeled 4 days after the initial insult by intrahippocampal injection of a retroviral vector encoding green fluorescent protein and newborn neurons were morphologically analyzed using a semiautomatic Neurolucida system and confocal laser scanning microscopy at 6 weeks.

RESULTS

Approximately 5% to 10% of newborn granule cells displayed significant morphological abnormalities comprising additional basal dendrites and, after middle cerebral artery occlusion, also ectopic cell position. The extent of morphological abnormalities was higher after large territorial infarcts and seems to depend on the severity of ischemic damage. An increased portion of mushroom spines in aberrant neurons suggests stable synaptic integration. However, poststroke generated granule cells with regular appearance also demonstrate alterations in dendritic complexity and spine morphology.

CONCLUSIONS

The remarkable stimulation of dentate neurogenesis after stroke coincides with an increased rate of aberrantly integrated neurons, which may contribute to functional impairments and, hypothetically, favor pathogenesis of adjustment disorders, cognitive deficits, or epilepsy often seen in stroke patients.

New insights into the role of hilar ectopic granule cells in the dentate gyrus based on quantitative anatomic analysis and three-dimensional reconstruction

The dentate gyrus is one of two main areas of the mammalian brain where neurons are born throughout adulthood, a phenomenon called postnatal neurogenesis. Most of the neurons that are generated are granule cells (GCs), the major principal cell type in the dentate gyrus. Some adult-born granule cells develop in ectopic locations, such as the dentate hilus. The generation of hilar ectopic granule cells (HEGCs) is greatly increased in several animal models of epilepsy and has also been demonstrated in surgical specimens from patients with intractable temporal lobe epilepsy (TLE). Herein we review the results of our quantitative neuroanatomic analysis of HEGCs that were filled with Neurobiotin following electrophysiologic characterization in hippocampal slices. The data suggest that two types of HEGCs exist, based on a proximal or distal location of the cell body relative to the granule cell layer, and based on the location of most of the dendrites, in the molecular layer or hilus. Three-dimensional reconstruction revealed that the dendrites of distal HEGCs can extend along the transverse and longitudinal axis of the hippocampus. Analysis of axons demonstrated that HEGCs have projections that contribute to the normal mossy fiber innervation of CA3 as well as the abnormal sprouted fibers in the inner molecular layer of epileptic rodents (mossy fiber sprouting). These data support the idea that HEGCs could function as a "hub" cell in the dentate gyrus and play a critical role in network excitability.

Hydroxynonenal-generated crosslinking fluorophore accumulation in Alzheimer disease reveals a dichotomy of protein turnover

Lipid peroxidation generates reactive aldehydes, most notably hydroxynonenal (HNE), which covalently bind amino acid residue side chains leading to protein inactivation and insolubility. Specific adducts of lipid peroxidation have been demonstrated in intimate association with the pathological lesions of Alzheimer disease (AD), suggesting that oxidative stress is a major component of AD pathogenesis. Some HNE-protein products result in protein crosslinking through a fluorescent compound similar to lipofuscin, linking lipid peroxidation and the lipofuscin accumulation that commonly occurs in post-mitotic cells such as neurons. In this study, brain tissue from AD and control patients was examined by immunocytochemistry and immunoelectron microscopy for evidence of HNE-crosslinking modifications of the type that should accumulate in the lipofuscin pathway. Strong labeling of granulovacuolar degeneration (GVD) and Hirano bodies was noted but lipofuscin did not contain this specific HNE-fluorophore. These findings directly implicate lipid crosslinking peroxidation products as accumulating not in the lesions or the lipofuscin pathways, but instead in a distinct pathway, GVD, that accumulates cytosolic proteins.

Activation of caspase-3 and c-Jun NH2-terminal kinase signaling pathways involving heroin-induced neuronal apoptosis

Heroin has been shown to cause spongiform leukoencephalopathy (SLE) in heroin addicts. In this study, we found that heroin could induce apoptosis of primary cultured cerebellar granule cells (CGC) and c-Jun N-terminal kinase (JNK) pathway is activated during CGCs apoptosis. Inhibiting JNK with a specific inhibitor, SP600125, reduced the levels of c-Jun phosphorylation and caspase-3 activation. We also showed that use the JNK inhibitor SP600125, caspase inhibitor z-VAD, or use SP600125 and z-VAD together significantly suppressed cell death induced by heroin. These results indicate that JNK pathway is an important mediator of the neurotoxic effects of heroin and inhibiting JNK activity may represent a new and effective strategy to treat heroin-induced SLE.

Granular expression of prolyl-peptidyl isomerase PIN1 is a constant and specific feature of Alzheimer's disease pathology and is independent of tau, Aβ and TDP-43 pathology

Alzheimer's disease (AD) manifests with progressive memory loss and decline of spatial awareness and motor skills. Neurofibrillary tangles (NFTs) represent one of the pathological hallmarks of AD. Previous studies suggest that the enzyme prolyl-peptidyl cis-trans isomerase PIN1 [protein interacting with NIMA (never in mitosis A)-1] recognizes hyperphosphorylated tau (in NFTs) and facilitates its dephosphorylation, thereby recovering its function. This study aims to determine the frequency, severity and distribution of PIN1 immunoreactivity and its relationship to NFTs and other neuropathological markers of neurodegeneration such as amyloid-β (Aβ) plaques and transcription-responsive DNA-binding protein of M(r) 43 kDa (TDP-43). Immunohistochemical analysis of 194 patients (46 with AD, 43 with Parkinson's disease/dementia with Lewy bodies, 12 with progressive supranuclear palsy/corticobasal degeneration, 36 with frontotemporal lobar degeneration, 21 with motor neuron disease and 34 non-demented (ND) individuals) revealed an increased frequency and severity of PIN1 immunoreactive inclusions in AD as compared to all diagnostic groups (P < 0.001). The hippocampal and cortical distribution of PIN1 granules was distinct from that of NFTs, Aβ and TDP-43 pathologies, though the frequency of neurons with PIN1 immunoreactivity increased with increasing NFT pathology. There was a progressive increase in PIN1 changes in ND individuals as the degree of AD-type pathological changes increased. Present findings indicate that PIN1 changes are a constant feature of AD pathology and could serve as a biomarker of the onset or spread of AD neuropathology independent of tau or Aβ.

[Morphology and cytochemistry of abnormal cytoplasmic granules in blood leukocytes in sapphire minks (cytological and cytochemical study)]

Detailed morphological and cytochemical investigation of blood leukocytes was performed in minks of three genotypes: dark-brown minks (n=10), which had the color resembling that of the wild type, mutant silver-blue (p/p) minks (n=10), and sapphire minks (a/a p/p) (n=10). The sapphire minks were demonstrate to have a hereditary defect of leukocyte granules containing peroxidase, nonspecific esterases and non-enzymatic cationic protein. These granules have abnormally large size, the neutrophil cytoplasm contains one to several abnormal granules, they are numerous in eosinophil and basophil cytoplasm and rare in lymphocytes and monocytes. Morphological and cytochemical features indicate the similarity of hereditary leukocytes pathology of sapphire mink with that one found in human Chediak-Higashi syndrome.

A case of prostatic adenocarcinoma with Paneth cell-like appearance

Paneth cell-like appearance of prostatic carcinoma cells with eosinophilic cytoplasmic granules is rarely reported, and is known to be associated with neuroendocrine differentiation of carcinoma cells. We report a case of prostatic adenocarcinoma with Paneth cell-like appearance that was localized next to conventional adenocarcinoma, and demonstrate its neuroendocrine differentiation by using immunohistochemical analysis. Paneth cell-like appearance of prostatic carcinoma cells should be recognized and considered as a sign of neuroendocrine differentiation due to the possible association with resistance to hormone therapy.

Paneth cell-like eosinophilic cytoplasmic granules in breast carcinoma

Prominent coarse eosinophilic cytoplasmic granules reminiscent of those in intestinal Paneth cells are rarely identified in breast carcinomas. In the literature, this phenomenon seems to be associated with acinic cell carcinoma of the breast or microglandular adenosis-related lesions. In this study, we report 3 breast carcinoma cases with such granules. Two of the cases were carcinomas arising in microglandular adenosis, one of which contained areas of acinic carcinoma-like features. The other case was a mammary carcinoma with prominent microglandular adenosis and also acinic cell carcinoma growth patterns. In the latter case, the patient had a history of neoadjuvant chemotherapy; and cells with coarse granules were found in both the pretreatment and posttreatment specimens. Although all 3 tumors were negative for HER2/neu, 2 tumors were estrogen receptor/progesterone receptor negative and one was estrogen receptor/progesterone receptor positive. Follow-up for 2 patients at 12 months and 3 years showed no evidence of disease, and the other patient died of her disease at 34 months. We provide a review of the literature and conclude that prominent coarse eosinophilic granules are a rare and nonspecific feature in breast epithelium. The clinical significance remains to be investigated, given the limited experience.

Distribution of lysosome-associated membrane proteins-1 and -2, and cathepsin D in eosinophilic granular bodies: possible relationship to cyst development in pilocytic astrocytomas

Pilocytic astrocytomas are usually cystic; cyst formation within these tumours may result in increased intracranial pressure, due to the effect of their mass, and contribute to cerebral damage. Eosinophilic granular bodies (EGBs) are produced abundantly in pilocytic astrocytomas but their role in disease progression remains unknown. Immunohistochemistry studies showed EGBs to exhibit pronounced reactivity to antibodies against lysosome-associated membrane proteins (LAMP)-1 and LAMP-2, and the lysosomal enzyme cathepsin D. Both LAMP-1 and LAMP-2 showed peripheral rim and granular staining patterns. The EGBs were scattered widely across cysts and, where EGBs aggregated in clusters, were usually close to areas of fluid in the cysts. Most EGBs had nuclei either attached or close by, indicating that the EGBs may be derived from anucleated astrocytes. The results suggest that EGBs, together with other factors, may play a role in the development of cysts in pilocytic astrocytomas.

Plugs clog the glandular outlets in fundic gland polyps

A systematic histologic analysis of 62 gastric fundic gland polyps (FGP) was carried out. All FGP (100%) showed foveolar cells with hypertrophic cytoplasm. In 95% of the FGP, parietal cells ballooned into the lumen and in 93%, exfoliated anucleated structures with eosinophilic granules were found. Plugs of anucleated structures with eosinophilic granules, most likely derived from exfoliated parietal cells, were found to clog the outlets of the glands in 86% of the FGP. None of the 30 control gastric biopsies without FGP had similar cellular aberrations. FGP seems to evolve by cellular aberrations affecting parietal cells. This is not surprising considering that genetic mutations are recorded in FGP with a common APC/b-catenin pathway in both FAP and sporadic cases. The genetic mutations in FGP might alter the biological behavior of the parietal cells, leading to increased exfoliation with clogging of the outlets of the glands. Thus, the blocking of the glandular outflow by plugs of anucleated structures with eosinophilic granules is the most likely cause for the cystic accumulation of "normal" glandular secretions.

A ‘touch’ of the White platelet syndrome

Investigations into structural defects in platelets from a large family with the White platelet syndrome (WPS) separated the members into three groups. The first group of 22 members was the subject of our first report (White JG, Key NS, King RA, Vercellotti GM. The white platelet syndrome: A new autosomal dominant platelet disorder. Platelets 2004;15:173-184). A third group of 13 members had no abnormalities of platelet ultrastructure. The second group of 17 members, the focus of the present study, had a 'touch' of the WPS. Platelet counts, mean platelet volumes (MPVs) and platelet responses to aggregating agents were normal in 'touch' patients in contrast to platelets of those with the full WPS in whom these parameters were abnormal. Up to 13% of the full WPS platelets contained large, fully developed Golgi complexes, up to seven in number, extruding innumerable vesicles from the trans-Golgi face and filling the cytoplasm of many platelets. Many Golgi complexes had centrioles associated with them. 'Touch' platelets had one or two Golgi complexes of intermediate size in 3-5% of their platelets. Golgi vesicles were uncommon and centrioles absent. Gray platelets and hypogranular cells were infrequent in patients with a 'touch' of the WPS, whereas up to 44% of the platelets from those with the WPS were gray or hypogranular. Elements of the dense tubular system were prominent in full WPS platelets, together with their formation into areas of cytoplasmic sequestration and autodigestion. These features were absent in 'touch' platelets. As commonly observed in full WPS platelets, mitochondria were larger and more numerous than alpha granules in some 'touch' cells. Both 'touch' and full WPS platelets frequently contained giant and rod-shaped granules. Dense bodies, however, were normal in size and number in 'touch' platelets, and half normal size in full WPS platelets. The separation of ultrastructural abnormalities in the two varieties of the WPS suggests that genetic defects involve more than a single gene and the genes are variable in their penetrance. Genetic studies to determine if this is the case are currently in progress.

Irritated seborrheic keratosis with coarse keratohyalin granules

AIMS

The viral etiology of certain types of seborrheic keratosis (SK) has been a controversial subject in literature, with different molecular results. On the contrary, to the molecular approach, some have suggested that certain types of SK are indeed warts, due to their morphologic features. We decided to investigate the presence of coarse keratohyalin granules in cases of irritated SK.

MATERIAL, METHODS AND RESULTS

We examined the last 60 cases with such a diagnosis in our Service of Anatomic Pathology and found these granules in eight cases (7.5%). The granules were evidenced in squamous eddies in four cases, while they were seen in foci of hypergranulosis from the top part of the epidermis in five cases. These granules were evidenced in a few foci in three cases while they were seen in multiple foci in five cases. In these eight cases, we also looked for other morphologic signs suggesting a viral origin, such as papilated, exo-endophytic configuration, parakeratosis at the tips of digitations, dilated vessels in the papillae and koilocytes. While six cases presented at least any of these other features, in two of the eight cases (25%), the only clue suggesting a viral origin was the evidence of the thick granules of keratohyalin.

CONCLUSIONS

We discuss the meaning of such a finding as described in literature, and conclude that it should be a specific feature to look out for, in cases of irritated SK, in order to exclude a diagnosis of verruca vulgaris.

The role of Rab38 in platelet dense granule defects

BACKGROUND

The fawn-hooded hypertensive (FHH) rat has a mutation in the Rab38 gene that is associated with a platelet dense granule storage pool disease.

OBJECTIVE

To better characterize the expression and function of Rab38 in FHH rat and human megakaryocytes and platelets.

PATIENTS AND METHODS

Rab38 expression in FHH rat and normal tissues was demonstrated by western blotting. Platelet and megakaryocyte morphology and Rab38 expression were examined by transmission electron microscopy and by immunofluorescence confocal microscopy. Platelet surface glycoprotein and P-selectin expression and total serotonin content were assessed by flow cytometry.

RESULTS

Rab38 was not expressed in FHH rat tissues, and FHH rat platelets and megakaryocytes lacked dense granules. FHH rat platelets had normal expression of surface glycoproteins and of surface P-selectin in response to thrombin. The total serotonin content in FHH rat platelets was similar to that in Brown Norway rat platelets. In a megakaryocyte cell line, Rab38 was expressed in a granular perinuclear and cytoplasmic pattern. There was partial colocalization with serotonin, and minimal colocalization with von Willebrand factor and lysosomal proteins.

CONCLUSIONS

The lack of Rab38 expression in the FHH rat results in the absence of normal dense granules in the megakaryocytes and platelets, which have otherwise normal structure and function. Rab38 may play a role in the development of dense granules in the megakaryocytes and platelets.

Prolonged exposures of cerebellar granule neurons to S-nitroso-N-acetylpenicillamine (SNAP) induce neuronal damage independently of peroxynitrite

Nitric oxide (NO) induces cell proliferation or cell death, depending on the cell type involved, the isoform of nitric oxide synthase activated, and its cellular localisation. In neurons, the damaging effect of NO is usually attributed to the highly toxic peroxynitrite, formed by its reaction with superoxide. Peroxynitrite induces DNA damage and consequently the activation of poly (ADP-ribose) polymerase (PARP). This study set out to examine the contribution of peroxynitrite to the damage induced in cerebellar granule neurons (CGNs) by treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), for short (6 h) or prolonged (24 h) exposures. The Alamar blue assay was used to quantify CGN viability, which was also assessed by morphological examination. SNAP (10 microM-1 mM) induced a concentration- and time-dependent reduction of CGN viability, with associated damage to cell bodies and neurite processes evident following 100 microM SNAP treatments. Damage from 6 h exposures was prevented by the presence of haemoglobin (a NO scavenger), uric acid (a peroxynitrite scavenger), melatonin (a non-specific antioxidant), and by cyclosporin A (a permeability transition pore blocker). It was reduced by the PARP-1 inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), whilst superoxide dismutase (SOD) potentiated the effects. Following 24 h exposure to SNAP, damage was only partially blocked by haemoglobin, melatonin, cyclosporin A and DPQ, but was not affected by uric acid or SOD. The data suggest that short exposure to NO induces neuronal damage through peroxynitrite produced by its interaction with superoxide, whereas a longer exposure to NO can induce damage partly by a mechanism which is independent of peroxynitrite formation.

Cytologic characteristics of intracytoplasmic refractile eosinophilic granular bodies in anaplastic oligodendroglioma: a case report

BACKGROUND

Oligodendrogliomas, which have a relatively better prognosis than tumors of the astrocytic lineage, have few morphologic clues for diagnosis.

CASE

To address this problem, eosinophilic refractile inclusions were examined cytologically in the tumor of a 59-year-old man, using surgical materials for rapid diagnosis. Cytologic, histologic, and immunohistochemical findings were compatible with the refractile eosinophilic inclusions found in oligodendroglial tumors. The tumor cells presented a sheet-like epithelial pattern, forming no overlapping cell clusters, with an ill-defined cytoplasmic membrane, and nuclei that appeared to be naked, approximately 2 times the size of a red blood cell (approximately 7 microm) in diameter. It was easier to examine the cells and inclusions by cytologic preparations than by histology.

CONCLUSION

The inclusions were thought to be a diagnostic clue for oligodendrogliomas, especially on cytology, and cytology was more useful than histology.