Tetraspanin-8 sequesters syntaxin-2 to control biphasic release propensity of mucin granules.

Agonist-mediated stimulated pathway of mucin and insulin release are biphasic in which rapid fusion of pre-docked granules is followed by slow docking and fusion of granules from the reserve pool. Here, based on a cell-culture system, we show that plasma membrane-located tetraspanin-8 sequesters syntaxin-2 to control mucin release. Tetraspanin-8 affects fusion of granules during the second phase of stimulated mucin release.

Defects in lipid homeostasis reflect the function of TANGO2 in phospholipid and neutral lipid metabolism.

We show that TANGO2 in mammalian cells localizes predominantly to mitochondria and partially at mitochondria sites juxtaposed to lipid droplets (LDs) and the endoplasmic reticulum. HepG2 cells and fibroblasts of patients lacking TANGO2 exhibit enlarged LDs. Quantitative lipidomics revealed a marked increase in lysophosphatidic acid (LPA) and a concomitant decrease in its biosynthetic precursor phosphatidic acid (PA).

The ulcerative colitis-associated gene FUT8 regulates the quantity and quality of secreted mucins.

Mucins are the main macrocomponents of the mucus layer that protects the digestive tract from pathogens. Fucosylation of mucins increases mucus viscoelasticity and its resistance to shear stress. These properties are altered in patients with ulcerative colitis (UC), which is marked by a chronic inflammation of the distal part of the colon.

Reactive oxygen species triggers unconventional secretion of antioxidants and Acb1.

Nutrient deprivation triggers the release of signal-sequence-lacking Acb1 and the antioxidant superoxide dismutase 1 (SOD1). We now report that secreted SOD1 is functionally active and accompanied by export of other antioxidant enzymes such as thioredoxins (Trx1 and Trx2) and peroxiredoxin Ahp1 in a Grh1-dependent manner. Our data reveal that starvation leads to production of nontoxic levels of reactive oxygen species (ROS).

New factors for protein transport identified by a genome-wide CRISPRi screen in mammalian cells.

Protein and membrane trafficking pathways are critical for cell and tissue homeostasis. Traditional genetic and biochemical approaches have shed light on basic principles underlying these processes. However, the list of factors required for secretory pathway function remains incomplete, and mechanisms involved in their adaptation poorly understood.

GRASP55 and UPR Control Interleukin-1β Aggregation and Secretion.

Signal-sequence-lacking interleukin (IL)-1β, is cleaved by caspase-1 to mature mIL-1β, which is secreted, without entering the endoplasmic reticulum. We report that macrophages of GRASP55 mice are defective in mIL-1β secretion and retain it as intracellular aggregates. Intriguingly, GRASP55 macrophages are defective in the IRE1α branch of the unfolded protein response.

Sodium channel TRPM4 and sodium/calcium exchangers (NCX) cooperate in the control of Ca-induced mucin secretion from goblet cells.

Regulated mucin secretion is essential for the formation of the mucus layer that protects the underlying epithelial cells from foreign particles. Alterations in the quantity or quality of secreted mucins are therefore detrimental to airway and colon physiology. Based on various biochemical assays in several human cell lines, we report here that Na/Ca exchanger 2 (NCX2) works in conjunction with transient receptor potential cation channel subfamily M member 4 (TRPM4), and perhaps TRPM5, Na channels to control Ca-mediated secretion of both mucin 2 (MUC2) and MUC5AC from HT29-18N2 colonic cancer cells.

KChIP3 coupled to Ca oscillations exerts a tonic brake on baseline mucin release in the colon.

Unlabelled: Regulated mucin secretion from specialized goblet cells by exogenous agonist-dependent (stimulated) and -independent (baseline) manner is essential for the function of the epithelial lining. Over extended periods, baseline release of mucin can exceed quantities released by stimulated secretion, yet its regulation remains poorly characterized. We have discovered that ryanodine receptor-dependent intracellular Ca oscillations effect the dissociation of the Ca-binding protein, KChIP3, encoded by gene, from mature mucin-filled secretory granules, allowing for their exocytosis.

A diacidic motif determines unconventional secretion of wild-type and ALS-linked mutant SOD1.

The nutrient starvation-specific unconventional secretion of Acb1 in requires ESCRT-I, -II, and -III and Grh1. In this study, we report that another signal sequence lacking cytoplasmic protein, superoxide dismutase 1 (SOD1), and its mutant form linked to amyotrophic lateral sclerosis (ALS), is also secreted by yeast upon nutrient starvation in a Grh1- and ESCRT-I-, -II-, and -III-dependent process. Our analyses reveal that a conserved diacidic motif (Asp-Glu) in these proteins is necessary for their export.

Role of Kif15 and its novel mitotic partner KBP in K-fiber dynamics and chromosome alignment.

Faithful segregation of the genetic material during the cell cycle is key for the continuation of life. Central to this process is the assembly of a bipolar spindle that aligns the chromosomes and segregates them to the two daughter cells. Spindle bipolarity is strongly dependent on the activity of the homotetrameric kinesin Eg5.

ESCRT-III drives the final stages of CUPS maturation for unconventional protein secretion.

The unconventional secretory pathway exports proteins that bypass the endoplasmic reticulum. In Saccharomyces cerevisiae, conditions that trigger Acb1 secretion via this pathway generate a Grh1 containing compartment composed of vesicles and tubules surrounded by a cup-shaped membrane and collectively called CUPS. Here we report a quantitative assay for Acb1 secretion that reveals requirements for ESCRT-I, -II, and -III but, surprisingly, without the involvement of the Vps4 AAA-ATPase.

TANGO1 recruits ERGIC membranes to the endoplasmic reticulum for procollagen export.

Previously we showed that membrane fusion is required for TANGO1-dependent export of procollagen VII from the endoplasmic reticulum (ER) (Nogueira, et al., 2014). Along with the t-SNARE Syntaxin 18, we now reveal the complete complement of SNAREs required in this process, t-SNAREs BNIP1 and USE1, and v-SNARE YKT6.

Brain-specific tryptophan hydroxylase, TPH2, and 5-HTTLPR are associated with frontal lobe symptoms in Alzheimer's disease.

A prospective, longitudinal study was set up to investigate possible genetic associations of behavioral and psychological signs and symptoms of dementia (BPSD) in Alzheimer's disease (AD) with two candidate genes in the serotonergic neurotransmitter pathway: serotonin transporter (SLC6A4) and brain-specific tryptophan hydroxylase (TPH2). Patients with probable AD (n = 249) were diagnosed according to NINCDS/ADRDA criteria. During follow-up, autopsy-confirmation of clinical diagnosis was obtained in 32 AD patients.

Genetic association of CR1 with Alzheimer's disease: a tentative disease mechanism.

CR1 is a novel Alzheimer's disease (AD) gene identified by genome-wide association studies (GWAS). Recently, we showed that AD risk could be explained by an 18-kilobase insertion responsible for the complement component (3b/4b) receptor 1 (CR1)-S isoform. We investigated the relevance of the CR1 isoforms to AD in a Canadian dataset.

Both common variations and rare non-synonymous substitutions and small insertion/deletions in CLU are associated with increased Alzheimer risk.

Background: We have followed-up on the recent genome-wide association (GWA) of the clusterin gene (CLU) with increased risk for Alzheimer disease (AD), by performing an unbiased resequencing of all CLU coding exons and regulatory regions in an extended Flanders-Belgian cohort of Caucasian AD patients and control individuals (n = 1930). Moreover, we have replicated genetic findings by targeted resequencing in independent Caucasian cohorts of French (n = 2182) and Canadian (n = 573) origin and by performing meta-analysis combining our data with previous genetic CLU screenings.

Results: In the Flanders-Belgian cohort, we identified significant clustering in exons 5-8 of rare genetic variations leading to non-synonymous substitutions and a 9-bp insertion/deletion affecting the CLU β-chain (p = 0.

Potent amyloidogenicity and pathogenicity of Aβ43.

The amyloid-β peptide Aβ42 is known to be a primary amyloidogenic and pathogenic agent in Alzheimer's disease. However, the role of Aβ43, which is found just as frequently in the brains of affected individuals, remains unresolved. We generated knock-in mice containing a pathogenic presenilin-1 R278I mutation that causes overproduction of Aβ43.

Amyloid precursor protein mutation E682K at the alternative β-secretase cleavage β'-site increases Aβ generation.

BACE1 cleaves the amyloid precursor protein (APP) at the β-cleavage site (Met(671) -Asp(672) ) to initiate the generation of amyloid peptide Aβ. BACE1 is also known to cleave APP at a much less well-characterized β'-cleavage site (Tyr(681) -Glu(682) ). We describe here the identification of a novel APP mutation E682K located at this β'-site in an early onset Alzheimer's disease (AD) case.

Rescue of progranulin deficiency associated with frontotemporal lobar degeneration by alkalizing reagents and inhibition of vacuolar ATPase.

Numerous loss-of-function mutations in the progranulin (GRN) gene cause frontotemporal lobar degeneration with ubiquitin and TAR-DNA binding protein 43-positive inclusions by reduced production and secretion of GRN. Consistent with the observation that GRN has neurotrophic properties, pharmacological stimulation of GRN production is a promising approach to rescue GRN haploinsufficiency and prevent disease progression. We therefore searched for compounds capable of selectively increasing GRN levels.

The CALHM1 P86L polymorphism is a genetic modifier of age at onset in Alzheimer's disease: a meta-analysis study.

The only established genetic determinant of non-Mendelian forms of Alzheimer's disease (AD) is the ε4 allele of the apolipoprotein E gene (APOE). Recently, it has been reported that the P86L polymorphism of the calcium homeostasis modulator 1 gene (CALHM1) is associated with the risk of developing AD. In order to independently assess this association, we performed a meta-analysis of 7,873 AD cases and 13,274 controls of Caucasian origin (from a total of 24 centers in Belgium, Finland, France, Italy, Spain, Sweden, the UK, and the USA).

Contribution of TARDBP to Alzheimer's disease genetic etiology.

The nuclear transactive response (TAR) DNA binding protein-43, TDP-43, is a major constituent of the ubiquitinated neuronal inclusions in patients with frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Missense mutations in TDP-43 have been associated with familial and sporadic ALS. Since TDP-43 immunoreactivity was also frequently observed in Alzheimer's disease (AD) brains and elevated TDP-43 plasma levels were detected in a subset of AD patients, we sequenced the TDP-43 gene, TARDBP, in a well-documented group of AD patients (n=485).

Role of progranulin as a biomarker for Alzheimer's disease.

Serum or plasma progranulin (GRN) is a highly accurate of GRN-related frontotemporal lobar degeneration, which is caused by loss-of-function mutations in the GRN gene. Both null mutations and missense mutations in GRN have also been observed in patients with Alzheimer's disease. Here, the evidence for a role of circulating GRN as a biochemical biomarker in neurodegeneration is reviewed, with a specific focus on its relevance in Alzheimer's disease.

Follow-up study of susceptibility loci for Alzheimer's disease and onset age identified by genome-wide association.

Replication of genetic association findings in independent studies represents an important validation tool in the search for susceptibility genes for complex diseases such as Alzheimer's disease (AD). In a well-characterized memory-clinic based study comprising 1078 unrelated AD patients and 652 control individuals, we set out to replicate previously reported genome-wide association of four novel risk SNPs with AD and onset age, with first stage p-values ranging from 0.001 to 0.

APP and BACE1 miRNA genetic variability has no major role in risk for Alzheimer disease.

Expression levels of the amyloid precursor protein (APP) and beta-site amyloid (Abeta) cleaving enzyme 1 (BACE1) have been implicated in Alzheimer disease (AD) progression. In a well-characterized Belgian group of 358 AD patients and 462 controls, we examined whether genetic variability in microRNA (miRNA) binding sites of APP and BACE1 or in associated miRNAs influenced risk for AD. Direct sequencing identified six variants in the 3' untranslated region (UTR) of APP and 29 variants in the 3' UTR of BACE1, of which few variants were restricted to patients: in APP; 4 variants in 6 patients ( approximately 2%) and in BACE1; 7 variants in 11 patients ( approximately 3.