Biology subjects

Molinaro, A.

Publications and source records attributed to Molinaro, A..

6 recordsLinked to original sources

bioRxiv2025

Cysteine-rich receptor-like kinases mediate Wall Teichoic Acid perception in Arabidopsis

Plants and animals detect microbe-associated molecular patterns (MAMPs) to initiate defense responses. Both lineages employ pattern recognition receptors (PRRs), yet plant mechanisms for sensing Gram-positive bacterial MAMPs remain poorly understood. Wall teichoic acids (WTAs), anionic glycopolymers unique to Gram-positive bacteria, are shown here to activate salicylic acid signaling, defense priming, and a non-canonical programmed cell death in Arabidopsis. We demonstrate that glycosylated WTAs from diverse Gram-positive species elicit these responses and provide genetic evidence that their recognition depends on two members of the plant-specific CYSTEINE-RICH RECEPTOR-LIKE KINASE (CRK) gene family, which is absent in animals and whose function remains elusive. These findings reveal WTAs as a novel class of MAMPs in plants and highlight CRKs as key components in their perception.

plant biology↗

bioRxiv2025

Lipopolysaccharides nanodiscs, a biomimetic platform to study bacterial surface.

Lipopolysaccharides (LPS) are essential components of the outer membranes of Gram-negative bacteria, playing a crucial role in antimicrobial resistance, virulence, and the hosts immune response. Self-assembled particles displaying LPS are essential for biophysical studies addressing the behavior of bacterial surfaces under specific biomimetic conditions. Styrene-maleic acid (SMA) copolymers were employed to form LPS nanodiscs, either from extracted LPS or directly from purified outer membranes. These nanodiscs, derived from pathogenic O157:H7 or laboratory E. coli strains, are well-defined in size and yield high-resolution nuclear magnetic resonance (NMR) spectra. They have been successfully used to investigate molecular recognition by a human C-type Lectin Receptor (CLR) of the immune system and interaction with polymyxin antibiotics using various biophysical methods. This study high-lights the significance of LPS nanodiscs as bacterial surface mimetics and opens promising avenues for further research into LPS structure and interactions. The ability to generate well-defined LPS nanodiscs offers a powerful tool for studying the molecular mechanisms underlying bacterial pathogenesis and immune response.

biophysics↗

bioRxiv2023

Adipocyte PI3K links adipostasis with insulin secretion through an adipoincretin effect

Insulin secretion is governed by insulin-PI3K signaling. Resolving the mechanism of this feedback is necessary to understand how insulin operates. Mice lacking the insulin receptor, or AKT1 and AKT2 in adipocytes, are severely lipoatrophic. Thus, the role of adipocyte insulin-PI3K signaling in the control of insulin secretion remains unknown. Using adipocyte- specific PI3K knockout mice (PI3KAdQ) and a panel of isoform-selective PI3K inhibitors, we have found that PI3K and PI3K{beta} activities are functionally redundant in adipocyte insulin signaling. PI3K{beta}-selective inhibitors had no effect on adipocyte AKT phosphorylation in control mice but blunted AKT phosphorylation specifically in adipocytes of PI3KAdQ mice, demonstrating adipocyte-selective inhibition of PI3K signaling. Adipocyte-selective PI3K inhibition increased serum FFA and potently induced insulin secretion. We name this phenomenon the adipoincretin effect. The adipoincretin effect was dissociated from blood glucose and blood glucose counterregulatory response. The contribution of lipolysis, lipid, and amino acid metabolism, and selected adipokines to the adipoincretin effect has been investigated. We conclude that basal insulin secretion is chiefly controlled by adipocyte PI3K signaling through the adipoincretin effect. This phenomenon reveals an essential role for adipocyte insulin-PI3K signaling in linking the rates of adipose tissue lipolysis with baseline insulin secretion during fasting.

physiology↗

bioRxiv2023

The unique three-dimensional arrangement of Macrophage Galactose Lectin enables E. coli LipoPolySaccharides recognition through two distinct interfaces

LipoPolySaccharides are a hallmark of Gram-negative bacteria and their presence at the cell surface is key for bacterial integrity. As surface exposed components, they are recognized by immunity C-type lectin receptors present on Antigen Presenting Cells. Human Macrophage Galactose Lectin binds E. coli surface that presents a specific glycan motif. Nevertheless, this high affinity interaction occurs regardless of the integrity of its canonical calcium-dependent glycan binding site. Nuclear Magnetic Resonance of MGL carbohydrate recognition domain and complete extracellular domain revealed a new glycan binding site opposite to the canonical site. A model of trimeric Macrophage Galactose Lectin was determined based on a combination of Small Angle X-ray scattering and Alphafold. A disulphide bond positions the Carbohydrate Recognition Domain perpendicular to the coiled-coil domain. This unique configuration for a C-type lectin orients the six glycan sites of MGL in an ideal position to bind LipoPolySaccharides at the bacterial surface with high avidity.

biophysics↗

bioRxiv2020

Timed mesodermal FGF and BMP govern the multi-step thyroid specification

Thyroid tissue is the site for de novo synthesis of thyroid hormones which are essential for vertebrate development and growth. Defects in embryonic thyroid morphogenesis are a predominant cause for congenital thyroid diseases but the molecular pathomechanisms are incompletely understood. The first molecularly recognizable step of thyroid development is the specification of thyroid precursors at a defined position in the anterior foregut endoderm. While recent studies identified FGF and BMP pathways as critical signaling factors for thyroid specification, the interplay between extrinsic signaling cues and thyroid transcription factor expression remained elusive. Here, we used zebrafish embryos to decipher the dynamics of thyroid transcription factor induction in relation to FGF and BMP signaling activities in pharyngeal endoderm. We first identified a previously unrecognized endodermal thyroid progenitor cell population expressing Pax2a but not Nkx2.4b. This cell population is characterized by enhanced FGF signaling but initially lacks detectable BMP signaling. A subpopulation of Pax2a-expressing progenitors differentiates subsequently into thyroid lineage-committed precursor cells co-expressing Pax2a and Nkx2.4b. We next combined pharmacological approaches with genetic models permitting inhibition or ectopic overactivation of signaling pathways to timely manipulate FGF and BMP activities. These experiments support a model where FGF signaling primarily regulates Pax2a expression whereas BMP signaling has dual functions in regulation of both Pax2a and Nkx2.4b expression. Collectively, our data allow us to formulate a refined model of thyroid cell specification from foregut endoderm.

developmental biology↗

bioRxiv2020

Novel ACE2-Independent Carbohydrate-Binding of SARS-CoV-2 Spike Protein to Host Lectins and Lung Microbiota

The immediate call for translational research in the field of coronavirus disease (COVID-19) pandemic, needs new and unexplored angles to support and contribute to this important worldwide health problem. The aim of this study is to better understand the pathogenic mechanisms underlying COVID-19, deciphering the carbohydrate-mediated interactions of the SARS-CoV-2 spike protein. We studied the carbohydrate-binding receptors that could be important for viral entry and for immune-modulatory responses, and we studied the interactions of the spike protein with the host lung microbiota. Exploring solid-phase immunoassays, we evaluated the interactions between the SARS-CoV-2 spike protein and a library of 12 different human carbohydrate-binding proteins (C-type lectins and Siglecs) involved in binding, triggering and modulation of innate and adaptive immune-responses. We revealed a specific binding of the SARS-CoV-2 spike protein to the receptors DC-SIGN, MGL, Siglec-9 and Siglec-10 that are all expressed on myeloid immune cells. In addition, because the lung microbiota can promote or modulate viral infection, we studied the interactions between the SARS-CoV-2 spike protein and a library of Streptococcus pneumoniae capsular polysaccharides, as well as other bacterial glyco-conjugates. We show specific binding of the spike protein to different S. pneumoniae capsular polysaccharides (serotypes 19F and 23F but not to serotype 14). Moreover we demonstrated a specific binding of SARS-CoV-2 spike protein to the lipopolysaccharide from the opportunistic human pathogen Pseudomonas aeruginosa, one of the leading cause of acute nosocomial infections and pneumonia. Interestingly, we identified rhamnosylated epitopes as one of the discriminating structures in lung microbiota to bind SARS-CoV-2 spike protein. In conclusion, we revealed novel ACE2-independent carbohydrate-mediated interactions with immune modulating lectins expressed on myeloid cells, as well as host lung microbiota glyco-conjugates. Our results identified new molecular pathways using host lectins and signalling, that may contribute to viral infection and subsequent immune exacerbation. Moreover we identified specific rhamnosylated epitopes in lung microbiota to bind SARS-CoV-2, providing a hypothetical link between the presence of specific lung microbiota and SARS-CoV-2 infection and severity.

immunology↗