DIDO is necessary for the adipogenesis that promotes diet-induced obesity.

The prevalence of overweight and obesity continues to rise in the population worldwide. Because it is an important predisposing factor for cancer, cardiovascular diseases, diabetes mellitus, and COVID-19, obesity reduces life expectancy. Adipose tissue (AT), the main fat storage organ with endocrine capacity, plays fundamental roles in systemic metabolism and obesity-related diseases. Dysfunctional AT can induce excess or reduced body fat (lipodystrophy). Dido1 is a marker gene for stemness; gene-targeting experiments compromised several functions ranging from cell division to embryonic stem cell differentiation, both in vivo and in vitro. We report that mutant mice lacking the DIDO N terminus show a lean phenotype. This consists of reduced AT and hypolipidemia, even when mice are fed a high-nutrient diet. DIDO mutation caused hypothermia due to lipoatrophy of white adipose tissue (WAT) and dermal fat thinning. Deep sequencing of the epididymal white fat (Epi WAT) transcriptome supported Dido1 control of the cellular lipid metabolic process. We found that, by controlling the expression of transcription factors such as C/EBPα or PPARγ, Dido1 is necessary for adipocyte differentiation, and that restoring their expression reestablished adipogenesis capacity in Dido1 mutants. Our model differs from other lipodystrophic mice and could constitute a new system for the development of therapeutic intervention in obesity.

CD69 downregulates autoimmune reactivity through active transforming growth factor-beta production in collagen-induced arthritis.

CD69 is induced after activation of leukocytes at inflammatory sites, but its physiological role during inflammation remains unknown. We explored the role of CD69 in autoimmune reactivity by analyzing a model of collagen-induced arthritis (CIA) in WT and CD69-deficient mice. CD69-/- mice showed higher incidence and severity of CIA, with exacerbated T and B cell immune responses to type II collagen. Levels of TGF-beta1 and TGF-beta2, which act as protective agents in CIA, were reduced in CD69-/- mice inflammatory foci, correlating with the increase in the proinflammatory cytokines IL-1beta and RANTES. Local injection of blocking anti-TGF-beta antibodies increased CIA severity and proinflammatory cytokine mRNA levels in CD69+/+ but not in CD69-/- mice. Moreover, in vitro engagement of CD69 induced total and active TGF-beta1 production in Concanavalin A-activated splenocyte subsets, mouse and human synovial leukocytes, and Jurkat stable transfectants of human CD69 but not in the parental CD69 negative cell line. Our results show that CD69 is a negative modulator of autoimmune reactivity and inflammation through the synthesis of TGF-beta, a cytokine that in turn downregulates the production of various proinflammatory mediators.

Expression and distribution of MAL2, an essential element of the machinery for basolateral-to-apical transcytosis, in human thyroid epithelial cells.

Polarized transport of newly synthesized proteins to the apical surface of epithelial cells takes place by a direct pathway from the Golgi or by an indirect route involving the delivery of the protein to the basolateral surface, followed by its endocytosis and transport across the cell. The indirect pathway, named transcytosis, is also used to translocate external material across the cell. MAL, a raft-associated integral membrane protein required for the direct apical route, is known to be expressed in the thyroid epithelium. MAL2, a member of the MAL protein family, has been recently identified as an essential component of the machinery for the transcytotic route in human hepatoma cells. Herein, we have investigated the expression and distribution of MAL2 in the human thyroid. MAL2 mRNA species were detected in the thyroid. Immunohistochemical analysis of thyroid follicles indicated that, in contrast to MAL, which predominantly distributed to the Golgi region, MAL2 distributed to the apical membrane. Biochemical analysis in primary thyrocyte cultures indicated that MAL2 exclusively resides in raft membranes. Confocal immunofluorescence analysis of thyrocyte cultures revealed that MAL2 predominantly localized in a subapical endosome compartment that was positive for Rab11a. Alterations in MAL2 expression, distribution, and appearance were found in specific types of follicular cell-derived carcinomas. Although the role of MAL2 has not been directly addressed in this study, the simultaneous expression of MAL and MAL2 suggests that traffic to the apical membrane in thyrocytes may rely on MAL for the direct route and on MAL2 for the transcytotic pathway.

Expression of MAL, an integral protein component of the machinery for raft-mediated pical transport, in human epithelia.

The MAL protein is the only integral membrane protein identified as being an essential component of the machinery necessary for apical transport in the canine MDCK cell line, a paradigm of polarized epithelial cells. To characterize the range of human epithelia that use MAL-mediated pathways of transport, we performed an immunohistochemical survey of normal tissues using a monoclonal antibody (MAb) specific for the MAL protein. For comparison, different types of carcinoma were also analyzed. MAL, with a characteristic strong supranuclear granular distribution, was detected in specific types of normal epithelial cells throughout the respiratory system, the gastrointestinal and genitourinary tracts, and in exocrine and endocrine glands. Absorptive cells (e.g., enterocytes), and many different types of specialized secretory cells, either organized in discrete clusters (e.g., endocrine cells in the pancreas), gathered together in an endocrine gland (e.g., thyroid), interspersed with other cells in glands (e.g., parietal cells), or dispersed singly among other cells (e.g., type 2 pneumocytes) were positive for MAL. We also analyzed a series of epithelial renal and thyroid tumors and found alterations dependent on the particular histological type of tumor. These results open potential applications of the anti-MAL antibody for the characterization of neoplastic tissue.

Expression of MAL2, an integral protein component of the machinery for basolateral-to-apical transcytosis, in human epithelia.

MAL2, an integral membrane protein of the MAL family, is an essential component of the machinery necessary for the indirect transcytotic route of apical transport in human hepatoma HepG2 cells. To characterize the range of human epithelia that use MAL2-mediated pathways of transport, we carried out an immunohistochemical survey of normal tissues using a monoclonal antibody specific to the MAL2 protein. MAL2 expression was detected in specific types of normal epithelial cells throughout the respiratory system, the gastrointestinal and genitourinary tracts, in exocrine and endocrine glands, and in hepatocytes. Many different types of specialized secretory cells, either organized in discrete clusters (e.g., endocrine cells in the pancreas) or in endocrine glands (e.g., prostate), were also positive for MAL2. In addition to epithelial cells, peripheral neurons, mast cells, and dendritic cells were found to express MAL2. For comparison with normal epithelial tissue, different types of renal carcinoma were also analyzed, revealing alterations in MAL2 expression/distribution dependent on the particular histological type of the tumor. Our results allow the prediction of the existence of MAL2-based trafficking pathways in specific cell types and suggest applications of the anti-MAL2 antibody for the characterization of neoplastic tissue.

SUMO-SIM interactions regulate the activity of RGSZ2 proteins.

The RGSZ2 gene, a regulator of G protein signaling, has been implicated in cognition, Alzheimer's disease, panic disorder, schizophrenia and several human cancers. This 210 amino acid protein is a GTPase accelerating protein (GAP) on Gαi/o/z subunits, binds to the N terminal of neural nitric oxide synthase (nNOS) negatively regulating the production of nitric oxide, and binds to the histidine triad nucleotide-binding protein 1 at the C terminus of different G protein-coupled receptors (GPCRs). We now describe a novel regulatory mechanism of RGS GAP function through the covalent incorporation of Small Ubiquitin-like MOdifiers (SUMO) into RGSZ2 RGS box (RH) and the SUMO non covalent binding with SUMO-interacting motifs (SIM): one upstream of the RH and a second within this region. The covalent attachment of SUMO does not affect RGSZ2 binding to GPCR-activated GαGTP subunits but abolishes its GAP activity. By contrast, non-covalent binding of SUMO with RH SIM impedes RGSZ2 from interacting with GαGTP subunits. Binding of SUMO to the RGSZ2 SIM that lies outside the RH does not affect GαGTP binding or GAP activity, but it could lead to regulatory interactions with sumoylated proteins. Thus, sumoylation and SUMO-SIM interactions constitute a new regulatory mechanism of RGS GAP function and therefore of GPCR cell signaling as well.

La radiación solar en el laboratoriode dermatología: importancia de la fuente de luz, los filtros y laespectrometría. Un modelo de cultivo de queratinocitos / Solar radiation in the laboratory of dermatology: light source, filters and spectrometry analysis are relevant. A model with keratinocytes in culture

Introducción: Los estudios de fotobiología requieren fuentes de luz que imiten lo más posible la radiación solar si la intención es obtener resultados con un significado biológico real. Habitualmente se da poca importancia al espectro de emisión de las lámparas de radiación ultravioleta utilizadas en los estudios de fotobiología, pero pequeñas variaciones en el espectro pueden condicionar efectos biológicos distintos. Métodos: Hemos comparado el efecto sobre cultivos de queratinocitos humanos normales de dos sistemas de simulación solar mediante filtros (AM0 + AM1D frente al 81017) que modifican el espectro de emisión de una lámpara de xenón para asemejarla a la radiación solar. Resultados: Hemos comprobado que ambos sistemas presentaban espectros parecidos a la luz solar cenital. El sistema equipado con AM0 + AM1D emitía menor cantidad de radiación ultravioleta B (UVB, 280-320 nm) (4,1% frente a 7,5%) aunque gran parte se emitía en el rango de 280 a 300 nm (1,3% frente a 0,4%). Los estudios de daño en queratinocitos en cultivo mostraron que usando los filtros AM0 + AM1D se obtenía un daño celular intenso con dosis 30 veces menores que usando el filtro 81017 (0,065 J/cm2 UVB y 1,3 J/cm2 UVA frente a 3,2 J/cm2 UVB y 38 J/cm2 UVA). Conclusiones: Nuestros resultados apoyan la necesidad de describir con exactitud la espectrometría de las fuentes de luz usadas en los estudios de fotobiología, precisando especialmente la radiación UVB de banda corta (AU)