CDS2 expression regulates de novo phosphatidic acid synthesis.

CDS enzymes (CDS1 and 2 in mammals) convert phosphatidic acid (PA) to CDP-DG, an essential intermediate in the de novo synthesis of PI. Genetic deletion of CDS2 in primary mouse macrophages resulted in only modest changes in the steady-state levels of major phospholipid species, including PI, but substantial increases in several species of PA, CDP-DG, DG and TG. Stable isotope labelling experiments employing both 13C6- and 13C6D7-glucose revealed loss of CDS2 resulted in a minimal reduction in the rate of de novo PI synthesis but a substantial increase in the rate of de novo PA synthesis from G3P, derived from DHAP via glycolysis.

A genetic screen to uncover mechanisms underlying lipid transfer protein function at membrane contact sites.

Lipid transfer proteins mediate the transfer of lipids between organelle membranes, and the loss of function of these proteins has been linked to neurodegeneration. However, the mechanism by which loss of lipid transfer activity leads to neurodegeneration is not understood. In photoreceptors, depletion of retinal degeneration B (RDGB), a phosphatidylinositol transfer protein, leads to defective phototransduction and retinal degeneration, but the mechanism by which loss of this activity leads to retinal degeneration is not understood.

Immunogenicity of SARS-CoV-2 vaccines BBV152 (COVAXIN®) and ChAdOx1 nCoV-19 (COVISHIELD™) in seronegative and seropositive individuals in India: a multicentre, nonrandomised observational study.

Background: There are limited global data on head-to-head comparisons of vaccine platforms assessing both humoral and cellular immune responses, stratified by pre-vaccination serostatus. The COVID-19 vaccination drive for the Indian population in the age group 18-45 years began in April 2021 when seropositivity rates in the general population were rising due to the delta wave of COVID-19 pandemic during April-May 2021.

Methods: Between June 30, 2021, and Jan 28, 2022, we enrolled 691 participants in the age group 18-45 years across four clinical sites in India.

Challenges and opportunities for discovering the biology of rare genetic diseases of the brain.

Diseases of the human nervous system are an important cause of morbidity and mortality worldwide. These disorders arise out of multiple aetiologies of which rare genetic mutations in genes vital to nervous system development and function are an important cause. The diagnosis of such rare disorders is challenging due to the close overlap of clinical presentations with other diseases that are not of genetic origin.

IMPA1 dependent regulation of phosphatidylinositol 4,5-bisphosphate and calcium signalling by lithium.

Lithium (Li) is widely used as a mood stabilizer to treat bipolar affective disorder. However, the molecular targets of Li that underpin its therapeutic effect remain unresolved. Inositol monophosphatase (IMPA1) is an enzyme involved in phosphatidylinositol 4,5-bisphosphate (PIP) resynthesis after PLC signaling.

PI3P-dependent regulation of cell size and autophagy by phosphatidylinositol 5-phosphate 4-kinase.

Phosphatidylinositol 3-phosphate (PI3P) and phosphatidylinositol 5-phosphate (PI5P) are low-abundance phosphoinositides crucial for key cellular events such as endosomal trafficking and autophagy. Phosphatidylinositol 5-phosphate 4-kinase (PIP4K) is an enzyme that regulates PI5P in vivo but can act on both PI5P and PI3P in vitro. In this study, we report a role for PIP4K in regulating PI3P levels in Loss-of-function mutants of the only PIP4K gene show reduced cell size in salivary glands.

Structural rationale to understand the effect of disease-associated mutations on Myotubularin.

Myotubularin or MTM1 is a lipid phosphatase that regulates vesicular trafficking in the cell. The gene is mutated in a severe form of muscular disease, X-linked myotubular myopathy or XLMTM, affecting 1 in 50,000 newborn males worldwide. There have been several studies on the disease pathology of XLMTM, but the structural effects of missense mutations of MTM1 are underexplored due to the unavailability of a crystal structure.

AP2 Regulates Thickveins Trafficking to Attenuate NMJ Growth Signaling in .

Compromised endocytosis in neurons leads to synapse overgrowth and altered organization of synaptic proteins. However, the molecular players and the signaling pathways which regulate the process remain poorly understood. Here, we show that σ2-adaptin, one of the subunits of the AP2-complex, genetically interacts with Mad, Medea and Dad (components of BMP signaling) to control neuromuscular junction (NMJ) growth in Ultrastructural analysis of mutants show an accumulation of large vesicles and membranous structures akin to endosomes at the synapse.

Septins tune lipid kinase activity and PI(4,5)P turnover during G-protein-coupled PLC signalling in vivo.

Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P] hydrolysis by phospholipase C (PLC) is a conserved mechanism of signalling. Given the low abundance of PI(4,5)P, its hydrolysis needs to be coupled to resynthesis to ensure continued PLC activity; however, the mechanism by which depletion is coupled to resynthesis remains unknown. PI(4,5)P synthesis is catalyzed by the phosphorylation of phosphatidylinositol 4 phosphate (PI4P) by phosphatidylinositol 4 phosphate 5 kinase (PIP5K).

A human stem cell resource to decipher the biochemical and cellular basis of neurodevelopmental defects in Lowe syndrome.

Human brain development is a complex process where multiple cellular and developmental events are coordinated to generate normal structure and function. Alteration in any of these events can impact brain development, manifesting clinically as neurodevelopmental disorders. Human genetic disorders of lipid metabolism often present with features of altered brain function.

Emerging perspectives on multidomain phosphatidylinositol transfer proteins.

The phosphatidylinositol transfer protein domain (PITP) is an evolutionarily conserved protein that is able to transfer phosphatidylinositol between membranes in vitro and in vivo. However some animal genomes also include genes that encode proteins where the PITP is found in cis with a number of additional domains and recent large scale genome sequencing efforts indicate that this type of multidomain architecture is widespread in the animal kingdom. In Drosophila photoreceptors, the multidomain phosphatidylinositol transfer protein RDGB is required to regulate phosphoinositide turnover during G-protein activated phospholipase C signalling.

Emerging cell biological functions of phosphatidylinositol 5 phosphate 4 kinase.

The generation of phosphoinositides (PIs) with spatial and temporal control is a key mechanism in cellular organization and signaling. The synthesis of PIs is mediated by PI kinases, proteins that are able to phosphorylate unique substrates at specific positions on the inositol headgroup to generate signaling molecules. Phosphatidylinositol 5 phosphate 4 kinase (PIP4K) is one such lipid kinase that is able to specifically phosphorylate phosphatidylinositol 5 phosphate, the most recently discovered PI to generate the well-known and abundant PI, phosphatidylinositol 4,5 bisphosphate [PI(4,5)P].

Interdomain interactions regulate the localization of a lipid transfer protein at ER-PM contact sites.

During phospholipase C-β (PLC-β) signalling in photoreceptors, the phosphatidylinositol transfer protein (PITP) RDGB, is required for lipid transfer at endoplasmic reticulum (ER)-plasma membrane (PM) contact sites (MCS). Depletion of RDGB or its mis-localization away from the ER-PM MCS results in multiple defects in photoreceptor function. Previously, the interaction between the FFAT motif of RDGB and the integral ER protein dVAP-A was shown to be essential for accurate localization to ER-PM MCS.

Label-Free Quantification of Phosphoinositides in Drosophila by Mass Spectrometry.

Phosphoinositides (PIs), the seven phosphorylated derivatives of phosphatidylinositol, are recognized as key molecules in the control of multiple molecular events in eukaryotic cells. Within cells, PIs are low-abundance lipids making their detection and quantification challenging. While many methods that allow radiolabeling and quantification of PIs in the context of cultured cells are available, these are not useful in the context of in vivo animal models where cell and developmental processes are best studied.

A genome engineering resource to uncover principles of cellular organization and tissue architecture by lipid signaling.

Phosphoinositides (PI) are key regulators of cellular organization in eukaryotes and genes that tune PI signaling are implicated in human disease mechanisms. Biochemical analyses and studies in cultured cells have identified a large number of proteins that can mediate PI signaling. However, the role of such proteins in regulating cellular processes and development in metazoans remains to be understood.

Extended synaptotagmin regulates membrane contact site structure and lipid transfer function in vivo.

Inter-organelle communication between closely apposed membranes is proposed at membrane contact sites (MCS). However, the regulation of MCS structure and their functional relevance in vivo remain debated. The extended synaptotagmins (Esyt) are evolutionarily conserved proteins proposed to function at MCS.

human stem cell derived cultures to monitor calcium signaling in neuronal development and function.

The development of the human brain involves multiple cellular processes including cell division, migration, and dendritic growth. These processes are triggered by developmental cues and lead to interactions of neurons and glial cells to derive the final complex organization of the brain. Developmental cues are transduced into cellular processes through the action of multiple intracellular second messengers including calcium.

A PI4KIIIα protein complex is required for cell viability during Drosophila wing development.

Phosphatidylinositol 4 phosphate (PI4P) and phosphatidylinositol 4,5 bisphosphate [PI(4,5)P] are enriched on the inner leaflet of the plasma membrane and proposed to be key determinants of its function. PI4P is also the biochemical precursor for the synthesis of PI(4,5)P but can itself also bind to and regulate protein function. However, the independent function of PI4P at the plasma membrane in supporting cell function in metazoans during development in vivo remains unclear.

A Genetic Screen in To Identify Novel Regulation of Cell Growth by Phosphoinositide Signaling.

Phosphoinositides are lipid signaling molecules that regulate several conserved sub-cellular processes in eukaryotes, including cell growth. Phosphoinositides are generated by the enzymatic activity of highly specific lipid kinases and phosphatases. For example, the lipid PIP, the Class I PI3 kinase that generates it and the phosphatase PTEN that metabolizes it are all established regulators of growth control in metazoans.