NSF ATPase and alpha-/beta-SNAPs disassemble the AMPA receptor-PICK1 complex

AMPA receptor (AMPAR) trafficking is crucial for synaptic plasticity that may be important for learning and memory. NSF and PICK1 bind the AMPAR GluR2 subunit and are involved in trafficking of AMPARs. Here, we show that GluR2, PICK1, NSF, and alpha-/beta-SNAPs form a complex in the presence of ATPgammaS. Similar to SNARE complex disassembly, NSF ATPase activity disrupts PICK1-GluR2 interactions in this complex. Alpha- and beta-SNAP have differential effects on this reaction. SNAP overexpression in hippocampal neurons leads to corresponding changes in AMPAR trafficking by acting on GluR2-PICK1 complexes. This demonstrates that the previously reported synaptic stabilization of AMPARs by NSF involves disruption of GluR2-PICK1 interactions. Furthermore, we are reporting a non-SNARE substrate for NSF disassembly activity.     

AMPA receptor tetramerization is mediated by Q/R editing

AMPA-type glutamate receptors (AMPARs) play a major role in excitatory synaptic transmission and plasticity. Channel properties are largely dictated by their composition of the four subunits, GluR1-4 (or A-D). Here we show that AMPAR assembly and subunit stoichiometry are determined by RNA editing in the pore loop. We demonstrate that editing at the GluR2 Q/R site regulates AMPAR assembly at the step of tetramerization. Specifically, edited R subunits are largely unassembled and ER retained, whereas unedited Q subunits readily tetramerize and traffic to synapses. This assembly mechanism restricts the number of the functionally critical R subunits in AMPAR tetramers. Therefore, a single amino acid residue affects channel composition and, in turn, controls ion conduction through the majority of AMPARs in the brain.     

An obstacle in preparing alloisoleucine

Alloisoleucine, prepared from a mixture of racemic isoleucine–alloisoleucine diastereoisomers, can be heavily contaminated with isoleucine if the recrystallization of acetyl-dl-alloisoleucine is controlled by melting point only. Two commercial specimens were found to be thus contaminated.     

BNIP3 Regulates AT101 [(-)-Gossypol] Induced Death in Malignant Peripheral Nerve Sheath Tumor Cells

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive Schwann cell-derived sarcomas and are the leading cause of mortality in patients with neurofibromatosis type 1 (NF1). Current treatment modalities have been largely ineffective, resulting in a high rate of MPNST recurrence and poor five-year patient survival. This necessitates the exploration of alternative chemotherapeutic options for MPNST patients. This study sought to assess the cytotoxic effect of the BH3-mimetic AT101 [(-)-gossypol] on MPNST cells in vitro and to identify key regulators of AT101-induced MPNST cell death. We found that AT101 caused caspase-independent, non-apoptotic MPNST cell death, which was accompanied by autophagy and was mediated through HIF-1α induced expression of the atypical BH3-only protein BNIP3. These effects were mediated by intracellular iron chelation, a previously unreported mechanism of AT101 cytotoxicity.     

Characterization of Calmodulin-Free Murine Inducible Nitric-Oxide Synthase

Nitric-Oxide Synthase (NOS), that produces the biological signal molecule Nitric-Oxide (NO), exists in three different isoforms called, neuronal (nNOS), endothelial (eNOS) and inducible (iNOS). All NOS isoforms require post-translational interaction with the calcium-binding protein, calmodulin (CaM) for manifesting their catalytic activity. However, CaM has been suggested to control the translational assembly of the enzyme as well, particularly in helping its inducible isoform, iNOS assume a stable, heme-replete, dimeric and active form. Expression of recombinant murine iNOS in E.coli in the absence of CaM has been previously shown to give extremely poor yield of the enzyme which was claimed to be absolutely heme-free, devoid of flavins, completely monomeric and catalytically inactive when compared to the heme-replete, active, dimeric iNOS, generated through co-expression with CaM. In contrast, we found that although iNOS expressed without CaM does produce significantly low amounts of the CaM-free enzyme, the iNOS thus produced, is not completely devoid of heme and is neither entirely monomeric nor absolutely bereft of catalytic activity as reported before. In fact, iNOS synthesized in the absence of CaM undergoes compromised heme incorporation resulting in extremely poor dimerization and activity compared to its counterpart co-expressed with CaM. Moreover, such CaM-free iNOS has similar flavin content and reductase activity as iNOS co-expressed with CaM, suggesting that CaM may not be as much required for the functional assembly of the iNOS reductase domain as its oxygenase domain. LC-MS/MS-based peptide mapping of the CaM-free iNOS confirmed that it had the same full-length sequence as the CaM-replete iNOS. Isothermal calorimetric measurements also revealed high affinity for CaM binding in the CaM-free iNOS and thus the possible presence of a CaM-binding domain. Thus CaM is essential but not indispensible for the assembly of iNOS and such CaM-free iNOS may help in elucidating the role of CaM on iNOS catalysis.     

Caring for Caregivers of People Living with HIV in the Family: A Response to the HIV Pandemic from Two Urban Slum Communities in Pune,India

Introduction

In low resource settings, the vast majority of ‘Person/people Living with HIV’ (PLHIV/s) and inadequate healthcare delivery systems to meet their treatment and care needs, caregivers play a vital role. Home based caregivers are often unrecognized with limited AIDS policies and programs focusing on them. We explored the perceptions and norms regarding care being provided by family caregivers of PLHIVs in India.

Methodology

A community based qualitative study to understand the issues pertaining to home based care for PLHIV was conducted in urban settings of Pune city, in Maharashtra, India. Eight Focus Group Discussions (FGDs) among men, women and peer educators were carried out. A total of 44 in-depth Interviews (IDIs) with PLHIVs (20) and their caregivers (24), were conducted using separate guides respectively. Data was analyzed thematically.

Results

Home based care was perceived as economically viable option available for PLHIVs. ‘Care’ comprised of emotional, adherence, nursing and financial support to PLHIV. Home based care was preferred over hospital based care as it ensured confidentiality and patient care without hampering routine work at home. Women emerged as more vital primary caregivers compared to men. Home based care for men was almost unconditional while women had no such support. The natal family of women also abandoned. Their marital families seemed to provide support. Caregivers voiced the need for respite care and training.

Discussion

Gender related stigma and discrimination existed irrespective of women being the primary family caregivers. The support from marital families indicates a need to explore care and support issues at natal and marital homes of the women living with HIV respectively. Home based care training and respite care for the caregivers is recommended. Gender sensitive interventions addressing gender inequity and HIV related stigma should be modeled while designing interventions for PLHIVs and their family caregivers.