Biology subjects

Garcia-Macia, M.

Publications and source records attributed to Garcia-Macia, M..

6 recordsLinked to original sources

bioRxiv2023

Weak neuronal glycolysis sustains cognition and organismal fitness

The energy cost of neuronal activity is mainly sustained by glucose1,2. However, in an apparent paradox, neurons only weakly metabolize glucose through glycolysis3,4,5,6, a circumstance that can be accounted for by the constant degradation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (Pfkfb3)3,7,8, a key glycolysis-promoting enzyme. To evaluate the in vivo physiological significance of this hypo-glycolytic metabolism, here we genetically engineered mice with their neurons transformed into active glycolytic cells through Pfkfb3 expression. In vivo molecular, biochemical, and metabolic flux analyses of these neurons revealed an accumulation of anomalous mitochondria, complex I disassembly, bioenergetic deficiency and mitochondrial redox stress. Notably, glycolysis-mediated NAD+ reduction impaired sirtuin-dependent autophagy. Furthermore, these mice displayed cognitive decline and a metabolic syndrome that was mimicked by confining Pfkfb3 expression to hypothalamic neurons. Neuron-specific genetic ablation of mitochondrial redox stress corrected these alterations. Thus, the weak glycolytic nature of neurons is required to sustain higher-order organismal functions.

cell biology↗

bioRxiv2022

CLN7 mutation causes aberrant redistribution of protein isoforms and contributes to Batten disease pathobiology

The variant late infantile form of the inherited neurodegenerative Batten disease (BD) is caused by mutations in the CLN7/MFSD8 gene and represents a strong candidate for gene therapy. Post-natal intracerebral administration of AAV9-hCLN7 to Cln7{Delta}ex2 knockout mice resulted in extended lifespan but dose escalation resulted in reduced acuity in neurophysiology tests, cerebral atrophy and elevated neuroinflammation. Comparing patient and control iPSC-derived neural progenitor cells (iNPC) we discovered that CLN7 localizes to the nucleus as well as the endolysosomal network and is differentially distributed in BD iNPC. Proteomics identified a profound nuclear defect in BD iNPC that compounds with mitochondrial and lysosomal metabolic defects resulting in elevated apoptosis. We further identified a 50kDa common nuclear CLN7 isoform and a 37kDa isoform that accumulates only in BD iNPC nuclei. Our findings suggest that successful treatment of CLN7 BD will require combinatorial therapies addressing both loss and aberrant gain of protein function.

cell biology↗

bioRxiv2020

Mitochondrial collapse links PFKFB3-promoted glycolysis with CLN7/MFSD8 neuronal ceroid lipofuscinosis pathogenesis

The neuronal ceroid lipofuscinoses (NCLs) are a family of monogenic life-limiting pediatric neurodegenerative disorders collectively known as Batten disease1. Although genetically heterogeneous2, NCLs share several clinical symptoms and pathological hallmarks such as lysosomal accumulation of lipofuscin and astrogliosis2,3. CLN7 disease belongs to a group of NCLs that present in late infancy4-6 and, whereas CLN7/MFSD8 gene is known to encode a lysosomal membrane glycoprotein4,7-9, the biochemical processes affected by CLN7-loss of function are unexplored thus preventing development of potential treatments1,10. Here, we found in the Cln7{Delta}ex2 mouse model11 of CLN7 disease that failure in the autophagy-lysosomal pathway causes accumulation of structurally and bioenergetically impaired, reactive oxygen species (ROS)-producing neuronal mitochondria that contribute to CLN7 pathogenesis. Cln7{Delta}ex2 neurons exhibit a metabolic shift mediated by pro-glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3). PFKFB3 inhibition in Cln7{Delta}ex2 mice in vivo and in CLN7 patients-derived cells rectified key disease hallmarks. Thus, specifically targeting glycolysis may alleviate CLN7 pathogenesis.

neuroscience↗

bioRxiv2019

Inhibiting the prostaglandin transporter PGT induces non-canonical thermogenesis at thermoneutrality

ABSTRACT / SUMMARYProstaglandins play fundamental roles in adipose tissue function. While prostaglandin F2 inhibits adipogenesis, prostaglandin E2 promotes adipose beiging. PGF2 and PGE2 are both inactivated through uptake by the plasma membrane transporter (PGT). We hypothesized that inhibiting PGT would increase PGF2 and PGE2 levels, thereby reducing white fat expansion and inducing beiging. Consistent with this hypothesis, inhibiting PGT in mice on high fat diet via genetic knockout or pharmacological blockade reduced body fat stores and induced thermogenesis at thermoneutrality. Inguinal white adipose tissue (iWAT) of these mice exhibited robust UCP1-independent thermogenesis characterized by mitochondrial expansion, coupling of O2 consumption to ATP synthesis, and induction of the creatine pathway. Enhanced coupled respiration persisted in PGT-KO iWAT adipocytes in a creatine shuttle-dependent manner. Thus, inhibiting PGT increases mitochondrial biogenesis and coupled respiration--each supported by the creatine pathway in a system lacking UCP1 expression--revealing PGT as a promising drug target against obesity.

physiology↗

bioRxiv2019

mTORC1-Plin3 pathway is essential to activate lipophagy and protects against hepatosteatosis.

During postprandial state, the liver is exposed to high levels of dietary fatty acids (FAs) and carbohydrates. FAs are re-esterified into triglycerides, which can be stored in lipid droplets (LDs) in the liver. Aberrant accumulation of LDs can lead to diseases such as alcoholic liver disease and non-alcoholic fatty liver disease, the latter being the most common liver pathology in western countries. Improved understanding of LD biology has potential to unlock new treatments for these liver diseases. The Perilipin (Plin) family is the group of proteins that coat LDs, controlling their biogenesis, stabilization, and preventing their degradation. Recent studies have revealed that autophagy is involved in LD degradation and, therefore, may be crucial to avoid lipid accumulation. Here, we show that a phosphorylated form of Plin3 is required for selective degradation of LDs in fibroblasts, primary hepatocytes and human liver slices. We demonstrate that oleic acid treatment induces the recruitment of the autophagy machinery to the surface of LDs. When Plin3 is silenced, this recruitment is suppressed resulting in accumulation of lipid. Plin3 pulldowns revealed interactions with the autophagy initiator proteins Fip200 and Atg16L indicating that Plin3 may function as a docking protein involved in lipophagy activation. Of particular importance, we define Plin3 as a substrate for mTORC1-dependent phosphorylation and show that this event is decisive for lipophagy. Our study therefore reveals that Plin3, and its phosphorylation by mTORC1, is crucial for degradation of LDs by autophagy. We propose that stimulating this pathway to enhance LD autophagy in hepatocytes will help protect the liver from lipid-mediated toxicity thus offering new therapeutic opportunities in human steatotic liver diseases.

cell biology↗

bioRxiv2019

Selective autophagy, lipophagy and mitophagy, in the Harderian gland along the estrous cycle: a potential retrieval effect of melatonin

Sexual dimorphism has been reported in many processes. However, sexual bias in favor of the use of males is very present in science. One of the main reasons is that the impact of hormones in diverse pathways and processes such as autophagy have not been properly addressed in vivo. The Harderian gland is a perfect model to study autophagic modulation as it exhibits important changes during the estrous cycle. The aim of this study is to identify the main processes behind Harderian gland differences under estrous cycle and their modulator. In the present study we show that redox-sensitive transcription factors have an essential role: NF-{kappa}B may activate SQSTM1/p62 in estrus, promoting selective types of autophagy: mitophagy and lipophagy. Nrf2 activation in diestrus, leads the retrieval phase and restoration of mitochondrial homeostasis. Melatonins receptors show higher expression in diestrus, leading to decreases in pro-inflammatory mediators and enhanced Nrf2 expression. Consequently, autophagy is blocked, and porphyrin release is reduced. All these results point to melatonin as one of the main modulators of the changes in autophagy during the estrous cycle.

cell biology↗