Lithium enhances secretion from large dense-core vesicles in nerve growth factor-differentiated PC12 cells

Ferricyanide-backfilled cylindrical carbon fiber microelectrodes for in vivo analysis with high stability and low polarized potential

A ferricyanide-backfilled cylindrical carbon fiber microelectrode of high stability and low polarized potential was fabricated and used for in vivo analysis.

Decreased cerebrospinal fluid secretogranin II concentrations in severe forms of bipolar disorder

BACKGROUND

Bipolar disorder is a common psychiatric mood disorder that is defined by recurrent episodes of abnormally elevated mood and depression. Progressive structural brain changes in individuals with bipolar disorder have been suggested to be associated with defects in the secretion of neurotrophic factors. We sought to assess how the regulated secretory pathway in the brain is affected in patients with bipolar disorder by measuring chromogranin B and secretogranin II, which are 2 cerebrospinal fluid (CSF) biological markers for this process.

METHODS

We measured the concentrations of chromogranin B (peptide 439-451) and secretogranin II (peptide 154-165) in the CSF of patients with well-defined bipolar disorder and healthy controls. The lifetime severity of bipolar disorder was rated using the Clinical Global Impression (CGI) scale.

RESULTS

We included 126 patients with bipolar disorder and 71 healthy controls in our analysis. Concentrations of secretogranin II were significantly lower in patients with bipolar disorder type I than in healthy controls. The reduction was most pronounced in patients with high CGI scores (i.e., severe disease).

LIMITATIONS

The cross-sectional design of the current study limits the ability to pinpoint the causalities behind the observed associations.

CONCLUSION

This study shows that the CSF marker secretogranin II has the potential to act as a biological marker for severe forms of bipolar disorder. Our findings indicate that patients with bipolar disorder possess defects in the regulatory secretory pathway, which may be of relevance to the progressive structural brain changes seen in those with severe forms of the disease.

Distinct domains in ORF52 tegument protein mediate essential functions in murine gammaherpesvirus 68 virion tegumentation and secondary envelopment

Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus are etiologically associated with several types of human malignancies. However, as these two human gammaherpesviruses do not replicate efficiently in cultured cells, the morphogenesis of gammaherpesvirus virions is poorly understood. Murine gammaherpesvirus 68 (MHV-68) provides a tractable model to define common, conserved features of gammaherpesvirus biology. ORF52 of MHV-68 is conserved among gammaherpesviruses. We have previously shown that this tegument protein is essential for the envelopment and egress of viral particles and solved the crystal structure of ORF52 dimers. To more closely examine its role in virion maturation, we performed immunoelectron microscopy of MHV-68-infected cells and found that ORF52 localized to both mature, extracellular virions and immature viral particles in the cytoplasm. ORF52 consists of three α-helices followed by one β-strand. To understand the structural requirements for ORF52 function, we constructed mutants of ORF52 and examined their ability to complement an ORF52-null MHV-68 virus. Mutations in conserved residues in the N-terminal α1-helix and C terminus, or deletion of the α2-helix, resulted in a loss-of-function phenotype. Furthermore, the α1-helix was crucial for the predominantly punctate cytoplasmic localization of ORF52, while the α2-helix was a key domain for ORF52 dimerization. Immunoprecipitation experiments demonstrated that ORF52 interacts with another MHV-68 tegument protein, ORF42; however, a single point mutation in R95 in the C terminus of ORF52 led to the loss of this interaction. Moreover, the homologues of MHV-68 ORF52 in Kaposi's sarcoma-associated herpesvirus and Epstein-Barr virus complement the defect in ORF52-null MHV-68 and interact with MHV-68 ORF52. Taken together, these data uncover the relationship between the α-helical structure and the molecular basis for ORF52 function. This is the first structure-based functional domain mapping study for an essential gammaherpesvirus tegument protein.

Neuropeptide Release is Impaired in a Mouse Model of Fragile X Mental Retardation Syndrome

Fragile X syndrome (FXS), an inherited disorder characterized by mental retardation and autismlike behaviors, is caused by the failure to transcribe the gene for fragile X mental retardation protein (FMRP), a translational regulator and transporter of select mRNAs. FXS model mice (Fmr1 KO mice) exhibit impaired neuropeptide release. Release of biogenic amines does not differ between wild-type (WT) and Fmr1 KO mice. Rab3A, an mRNA cargo of FMRP involved in the recruitment of vesicles, is decreased by ∼50% in synaptoneurosomes of Fmr1 KO mice; however, the number of dense-core vesicles (DCVs) does not differ between WT and Fmr1 KO mice. Therefore, deficits associated with FXS may reflect this aberrant vesicle release, specifically involving docking and fusion of peptidergic DCVs, and may lead to defective maturation/maintenance of synaptic connections.

In Vitro Electrochemistry of Biological Systems

This article reviews recent work involving electrochemical methods for in vitro analysis of biomolecules, with an emphasis on detection and manipulation at and of single cells and cultures of cells. The techniques discussed include constant potential amperometry, chronoamperometry, cellular electroporation, scanning electrochemical microscopy, and microfluidic platforms integrated with electrochemical detection. The principles of these methods are briefly described, followed in most cases with a short description of an analytical or biological application and its significance. The use of electrochemical methods to examine specific mechanistic issues in exocytosis is highlighted, as a great deal of recent work has been devoted to this application.

The PC12 cell as model for neurosecretion

This review attempts to touch on the history and application of amperometry at PC12 cells for fundamental investigation into the exocytosis process. PC12 cells have been widely used as a model for neural differentiation and as such they have been used to examine the effects of differentiation on exocytotic release and specifically release at varicosities. In addition, dexamethasone-differentiated cells have been shown to have an increased number of releasable vesicles with increased quantal size, thereby allowing for an even broader range of applications including neuropharmacological and neurotoxicological studies. PC12 cells exhibiting large numbers of events have two distinct pools of vesicles, one about twice the quantal size of the other and each about half the total releasable vesicles. As will be outlined in this review, these cells have served as an extremely useful model of exocytosis in the study of the latency of stimulation-release coupling, the role of exocytotic proteins in regulation of release, effect of drugs on quantal size, autoreceptors, fusion pore biophysics, environmental factors, health and disease. As PC12 cells have some advantages over other models for neurosecretion, including chromaffin cells, it is more than likely that in the following decade PC12 cells will continue to serve as a model to study exocytosis.

Murine gammaherpesvirus 68 ORF52 encodes a tegument protein required for virion morphogenesis in the cytoplasm

The tegument, a semiordered matrix of proteins overlying the nucleocapsid and underlying the virion envelope, in viruses in the gamma subfamily of Herpesviridae is poorly understood. Murine gammaherpesvirus 68 (MHV-68) is a robust model for studying gammaherpesvirus virion structure, assembly, and composition, as MHV-68 efficiently completes the lytic phase and productively infects cultured cells. We have found that MHV-68 ORF52 encodes an abundant tegument protein conserved among gammaherpesviruses. Detergent sensitivity experiments revealed that the MHV-68 ORF52 protein is more tightly bound to the virion nucleocapsid than the ORF45 tegument protein but could be dissociated from particles that retained the ORF65 small capsomer protein. ORF52, tagged with enhanced green fluorescent protein or FLAG epitope, localized to the cytoplasm. A recombinant MHV-68 bacterial artificial chromosome mutant with a nonsense mutation incorporated into ORF52 exhibited viral DNA replication, expression of late lytic genes, and capsid assembly and packaging at levels near those of the wild type. However, the MHV-68 ORF52-null virus was deficient in the assembly and release of infectious virion particles. Instead, partially tegumented capsids produced by the ORF52-null mutant accumulated in the cytoplasm, containing conserved capsid proteins, the ORF64 and ORF67 tegument proteins, but virtually no ORF45 tegument protein. Thus, ORF52 is essential for the tegumentation and egress of infectious MHV-68 particles in the cytoplasm, suggesting an important conserved function in gammaherpesvirus virion morphogenesis.