ABSTRACT
BACKGROUND: Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy due to mutations in the CAPN3 gene. While the pathophysiology of this disease has not been clearly established yet, Wnt and mTOR signaling pathways impairment in LGMDR1 muscles has been reported. RESULTS: A reduction in Akt phosphorylation ratio and upregulated expression of proteins implicated in glycolysis (HK-II) and in fructose and lactate transport (GLUT5 and MCT1) in LGMDR1 muscle was observed. In vitro analysis to establish mitochondrial and glycolytic functions of primary cultures were performed, however, no differences between control and patients were observed. Additionally, gene expression analysis showed a lack of correlation between primary myoblasts/myotubes and LGMDR1 muscle while skin fibroblasts and CD56- cells showed a slightly better correlation with muscle. FRZB gene was upregulated in all the analyzed cell types (except in myoblasts). CONCLUSIONS: Proteins implicated in metabolism are deregulated in LGMDR1 patients' muscle. Obtained results evidence the limited usefulness of primary myoblasts/myotubes for LGMDR1 gene expression and metabolic studies. However, since FRZB is the only gene that showed upregulation in all the analyzed cell types it is suggested its role as a key regulator of the pathophysiology of the LGMDR1 muscle fiber. The Wnt signaling pathway inactivation, secondary to FRZB upregulation, and GLUT5 overexpression may participate in the impaired adipogenesis in LGMD1R patients.
Subject(s)
Muscle Proteins , Muscular Dystrophies, Limb-Girdle , Humans , Muscle Proteins/genetics , Muscular Dystrophies, Limb-Girdle/genetics , Muscular Dystrophies, Limb-Girdle/metabolism , Muscle Fibers, Skeletal/metabolism , Wnt Signaling Pathway , Cell Culture Techniques , Muscle, Skeletal/metabolismABSTRACT
Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy produced by mutations in the CAPN3 gene. It is a rare disease and there is no cure or treatment for the disease while the pathophysiological mechanism by which the absence of calpain 3 provokes the dystrophy in muscles is not clear. However, key proteins implicated in Wnt and mTOR signaling pathways, which regulate muscle homeostasis, showed a considerable reduction in their expression and in their phosphorylation in LGMDR1 patients' muscles. Finally, the administration of tideglusib and VP0.7, ATP non-competitive inhibitors of glycogen synthase kinase 3ß (GSK-3ß), restore the expression and phosphorylation of these proteins in LGMDR1 cells, opening the possibility of their use as therapeutic options.
Subject(s)
Glycogen Synthase Kinase 3 beta/antagonists & inhibitors , Muscular Dystrophies, Limb-Girdle/drug therapy , Nerve Tissue Proteins/antagonists & inhibitors , Signal Transduction/drug effects , Adenosine Triphosphate/metabolism , Allosteric Site/drug effects , CD56 Antigen/analysis , Calpain/deficiency , Calpain/genetics , Fibroblasts/drug effects , Fibroblasts/metabolism , Gene Expression Regulation/drug effects , Glycogen Synthase Kinase 3 beta/chemistry , Humans , Hydrazines/pharmacology , Hydrazines/therapeutic use , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/metabolism , Muscle Fibers, Skeletal/drug effects , Muscle Fibers, Skeletal/metabolism , Muscle Proteins/deficiency , Muscle Proteins/genetics , Muscular Dystrophies, Limb-Girdle/enzymology , Nerve Tissue Proteins/chemistry , Phosphorylation , Protein Processing, Post-Translational/drug effects , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Proto-Oncogene Proteins c-akt/physiology , Quinolones/pharmacology , Quinolones/therapeutic use , TOR Serine-Threonine Kinases/antagonists & inhibitors , TOR Serine-Threonine Kinases/physiology , Thiadiazoles/pharmacology , Thiadiazoles/therapeutic use , Wnt Signaling Pathway/drug effectsABSTRACT
RTX (Repeats in ToXin) pore-forming toxins constitute an expanding family of exoproteins secreted by many Gram-negative bacteria and involved in infectious diseases caused by said pathogens. Despite the relevance in the host/pathogen interactions, the structure and characteristics of the lesions formed by these toxins remain enigmatic. Here, we capture the first direct nanoscale pictures of lytic pores formed by an RTX toxin, the Adenylate cyclase (ACT), secreted by the whooping cough bacterium Bordetella pertussis. We reveal that ACT associates into growing-size oligomers of variable stoichiometry and heterogeneous architecture (lines, arcs, and rings) that pierce the membrane, and that, depending on the incubation time and the toxin concentration, evolve into large enough "holes" so as to allow the flux of large molecular mass solutes, while vesicle integrity is preserved. We also resolve ACT assemblies of similar variable stoichiometry in the cell membrane of permeabilized target macrophages, proving that our model system recapitulates the process of ACT permeabilization in natural membranes. Based on our data we propose a non-concerted monomer insertion and sequential mechanism of toroidal pore formation by ACT. A size-tunable pore adds a new regulatory element to ACT-mediated cytotoxicity, with different pore sizes being putatively involved in different physiological scenarios or cell types.
