Endosomal trafficking ensures the proper distribution of lipids and proteins to various cellular compartments, facilitating intracellular communication, nutrient transport, waste disposal, and the ...maintenance of cell structure. Retromer, a peripheral membrane protein complex, plays an important role in this process by recruiting the associated actin‐polymerizing WASH complex to establish distinct sorting domains. The WASH complex is recruited through the interaction of the VPS35 subunit of retromer with the WASH complex subunit FAM21. Here, we report the identification of two separate fragments of FAM21 that interact with VPS35, along with a third fragment that binds to the VPS29 subunit of retromer. The crystal structure of VPS29 bound to a peptide derived from FAM21 shows a distinctive sharp bend that inserts into a conserved hydrophobic pocket with a binding mode similar to that adopted by other VPS29 effectors. Interestingly, despite the network of interactions between FAM21 and retromer occurring near the Parkinson's disease‐linked mutation (D620N) in VPS35, this mutation does not significantly impair the direct association with FAM21 in vitro.
Mutations in VAV1, a gene that encodes a multifunctional protein important for lymphocytes, are found at different frequencies in peripheral T‐cell lymphoma (PTCL), non‐small cell lung cancer, and ...other tumors. However, their pathobiological significance remains unsettled. After cataloguing 51 cancer‐associated VAV1 mutations, we show here that they can be classified in five subtypes according to functional impact on the three main VAV1 signaling branches, GEF‐dependent activation of RAC1, GEF‐independent adaptor‐like, and tumor suppressor functions. These mutations target new and previously established regulatory layers of the protein, leading to quantitative and qualitative changes in VAV1 signaling output. We also demonstrate that the most frequent VAV1 mutant subtype drives PTCL formation in mice. This process requires the concurrent engagement of two downstream signaling branches that promote the chronic activation and transformation of follicular helper T cells. Collectively, these data reveal the genetic constraints associated with the lymphomagenic potential of VAV1 mutant subsets, similarities with other PTCL driver genes, and potential therapeutic vulnerabilities.
Synopsis
VAV1 encodes a multifunctional signaling protein involved in both RAC1 GTPase activation and adaptor‐like functions. Mutations in this gene have recently been found in PTCL and other tumor types. Here, we have catalogued 51 VAV1 tumor‐associated mutations according to their functional impact on the downstream signaling branches of the protein. Our work has revealed that:
The VAV1 gain‐of‐function mutations belong to different subclasses according to impact on VAV1 downstream signaling.
These mutations target both expected and hitherto unknown VAV1 regulatory layers.
A VAV1 mutation representative of the most frequent functional subclass drives PTCL formation in mice.
VAV1‐driven lymphomagenesis requires cooperating signals from the catalytic‐dependent and independent pathways of the mutant protein.
The molecular features of VAV1‐driven lymphomas resemble those found in PTCL patients.
Systematic mapping of non‐passenger mutations in the multifunctional signaling factor VAV1 offers new insights into their signaling consequences and functional outcomes in vivo.
Architecture of the ESCPE-1 membrane coat Lopez-Robles, Carlos; Scaramuzza, Stefano; Astorga-Simon, Elsa N ...
Nature structural & molecular biology,
07/2023, Letnik:
30, Številka:
7
Journal Article
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Recycling of membrane proteins enables the reuse of receptors, ion channels and transporters. A key component of the recycling machinery is the endosomal sorting complex for promoting exit 1 ...(ESCPE-1), which rescues transmembrane proteins from the endolysosomal pathway for transport to the trans-Golgi network and the plasma membrane. This rescue entails the formation of recycling tubules through ESCPE-1 recruitment, cargo capture, coat assembly and membrane sculpting by mechanisms that remain largely unknown. Herein, we show that ESCPE-1 has a single-layer coat organization and suggest how synergistic interactions between ESCPE-1 protomers, phosphoinositides and cargo molecules result in a global arrangement of amphipathic helices to drive tubule formation. Our results thus define a key process of tubule-based endosomal sorting.
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•Meloxicam is efficiently in vitro transported by murine Abcg2 and human ABCG2.•Abcg2 transporter affects the oral pharmacokinetics of meloxicam in mice.•Abcg2 restricts brain ...accumulation of meloxicam in mice.•Abcg2 transporter plays a role in the secretion of meloxicam into milk in mice.
ATP-binding cassette (ABCG2) is an efflux transporter that extrudes xenotoxins from cells in liver, intestine, mammary gland, brain and other organs, affecting the pharmacokinetics, brain accumulation and secretion into milk of several compounds, including antitumoral, antimicrobial and anti-inflammatory drugs. The aim of this study was to investigate whether the widely used anti-inflammatory drug meloxicam is an Abcg2 sustrate, and how this transporter affects its systemic distribution. Using polarized ABCG2-transduced cell lines, we found that meloxicam is efficiently transported by murine Abcg2 and human ABCG2. After oral administration of meloxicam, the area under the plasma concentration–time curve in Abcg2−/− mice was 2-fold higher than in wild type mice (146.06 ± 10.57 µg·h/ml versus 73.80 ± 10.00 µg·h/ml). Differences in meloxicam distribution were reported for several tissues after oral and intravenous administration, with a 20-fold higher concentration in the brain of Abcg2−/− after oral administration. Meloxicam secretion into milk was also affected by the transporter, with a 2-fold higher milk-to-plasma ratio in wild-type compared with Abcg2−/− lactating female mice after oral and intravenous administration. We conclude that Abcg2 is an important determinant of the plasma and brain distribution of meloxicam and is clearly involved in its secretion into milk.
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