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The translocase of the outer mitochondrial membrane (TOM) is the main entry gate for proteins.sup.1-4. Here we use cryo-electron microscopy to report the structure of the yeast TOM core complex.sup.5-9 at 3.8-Å resolution. The structure reveals the high-resolution architecture of the translocator consisting of two Tom40 [beta]-barrel channels and [alpha]-helical transmembrane subunits, providing insight into critical features that are conserved in all eukaryotes.sup.1-3. Each Tom40 [beta]-barrel is surrounded by small TOM subunits, and tethered by two Tom22 subunits and one phospholipid. The N-terminal extension of Tom40 forms a helix inside the channel; mutational analysis reveals its dual role in early and late steps in the biogenesis of intermembrane-space proteins in cooperation with Tom5. Each Tom40 channel possesses two precursor exit sites. Tom22, Tom40 and Tom7 guide presequence-containing preproteins to the exit in the middle of the dimer, whereas Tom5 and the Tom40 N extension guide preproteins lacking a presequence to the exit at the periphery of the dimer. The high-resolution cryo-electron microscopy structure of the yeast translocase of the outer mitochondrial membrane reveals key features of mitochondrial protein import that are conserved in all eukaryotes., Author(s): Yuhei Araiso [sup.1] [sup.2] [sup.12] , Akihisa Tsutsumi [sup.3] , Jian Qiu [sup.4] [sup.5] [sup.13] , Kenichiro Imai [sup.6] , Takuya Shiota [sup.7] [sup.8] , Jiyao Song [sup.4] , [...]

The role of sinus macrophages (SMs) in anticancer immune responses has received considerable interest in recent years, but the types of molecules that are expressed in human SMs have not yet been clarified in detail. We therefore sought to identify dendritic cell (DC)– or macrophage‐related molecules in SMs in human lymph nodes (LNs). SMs are strongly positive for Iba‐1, CD163, CD169, and CD209. CD169 (clone SP216) reacted with almost all SMs, mainly in the cell surface membrane, while CD169 (clone HSn 7D2) reacted with a subpopulation of SMs, mainly in the cytoplasm, with a significant increase observed after IFN‐α stimulation. The immunoreactivity of clone HSn 7D2 was markedly reduced after transfection with small interfering RNA against CD169, while that of clone SP216 was slightly reduced. The induction of CCL8 and CXCL10 messenger RNA (mRNA) expression by IFN‐α was confirmed using cultured macrophages and RT‐qPCR, but fluorescence in situ hybridization did not detect CCL8 and CXCL10 mRNA expression in SMs. Single‐cell RNA sequence data of LNs indicated that the highest level of CXCL10 gene expression occurred in monocytes. In conclusion, we found that CD209, also known as DC‐related molecule, was expressed in human SMs. The heterogeneity observed in CD169 reacted with cone HSn 7D2 and SP216 was potentially due to the modification of CD169 protein by IFN stimulation. Further, no expression of CXCL10 mRNA in SMs suggested that SMs might be resident macrophages. [ABSTRACT FROM AUTHOR]

CD169+ macrophages are suggested to play a pivotal role in establishing anti-tumor immunity. They capture dead tumor cell-associated antigens and transfer their information to lymphocsytes, including CD8+ T cells, which is important for successful tumor suppression. This study aimed to determine the prognostic significance of CD169+ macrophages residing in the tumor-draining lymph nodes from cases of bladder cancer. In this retrospective study, 44 bladder cancer patients who received radical cystectomy were examined. The abundance of CD169+ macrophages in the regional lymph nodes and the number of CD8+ T cells in the primary tumor were investigated by immunohistochemistry. A CD169 score was calculated based on the intensity of CD169 staining and the proportion of CD169+ macrophages, and the scores were compared to the patients' clinicopathological parameters. A high CD169 score was significantly associated with low T stage and with a high number of CD8+ T cells infiltrating into the tumor. The group with high CD169 expression had significantly longer cancer-specific survival than the group with low CD169 expression (5-year cancer-specific survival rate: 83.3% vs 31.3%). In a multivariate analysis, the CD169 score was identified as a strong and independent favorable prognostic factor for cancer-specific survival. Our findings suggest that CD169+ macrophages in the lymph nodes enhance anti-tumor immunity by expanding CD8+ T cells in bladder cancer. The CD169 score may serve as a novel marker for the evaluation of bladder cancer prognosis. [ABSTRACT FROM AUTHOR]

Recent studies have indicated the clinical significance of tumor-associated macrophages ( TAM) in several malignant tumors including breast cancer. Although recent studies have focused on CD68-positive or CD163-positive TAM in breast cancer, no study has investigated the significance of CD204-positive TAM in breast cancer. We found that CD204 expression on macrophages was evaluated following stimulation with the conditioned medium ( CM) of breast cancer cell lines. Paraffin sections of 149 breast cancer samples which were diagnosed as invasive ductal carcinoma were immunohistochemically analyzed for CD68, CD163 and CD204 expression. The results of analyses indicated that a high number of CD204-positive TAM was associated with worse clinical prognoses, including relapse-free survival, distant relapse-free survival and breast cancer-specific survival; however, neither the numbers of CD68-positive or CD163-positive TAM were associated with clinical courses. Of the clinicopathological factors investigated, estrogen receptor, Ki-67 index, hormone subtype, and histological grade were significantly related to the increased number of CD163-positive and CD204-positive TAM. These data indicate the clinical significance of CD204-positive TAM in breast cancer progression and CD204 is a marker for predicting clinical prognosis in breast cancer. [ABSTRACT FROM AUTHOR]

Mitochondrial protein traffic requires precise recognition of the mitochondrial targeting signals by the import receptors on the mitochondrial surface including a general import receptor Tom20 and a receptor for presequence-less proteins, Tom70. Here we took a proteome-wide approach of mitochondrial protein import in vitro to find a set of presequence-containing precursor proteins for recognition by Tom70. The presequences of the Tom70-dependent precursor proteins were recognized by Tom20, whereas their mature parts exhibited Tom70-dependent import when attached to the presequence of Tom70-independent precursor proteins. The mature parts of the Tom70-dependent precursor proteins have the propensity to aggregate, and the presence of the receptor domain of Tom70 prevents their aggregate formation. Therefore Tom70 plays the role of a docking site for not only cytosolic chaperones but also aggregate-prone substrates to maintain their solubiity for efficient transfer to downstream components of the mitochondrial import machineries. [ABSTRACT FROM AUTHOR]

There are numerous macrophages and dendritic cells in lymph nodes (LNs). Recent studies have highlighted that sinus macrophages (SMs) in LNs possess antigen-presenting capabilities and are related to anti-cancer immune responses. In this study, we assessed the distribution of SMs in mesenteric LNs removed during surgery for colorectal cancer. A marked reduction of SMs was noted in elderly patients, particularly those over 80 years old. We observed a disappearance of CD169-positive cells in LNs where SMs were reduced. In silico analysis of publicly available single-cell RNA sequencing data from LNs revealed that CD169-positive macrophages express numerous genes associated with antigen presentation and lymphocyte proliferation, similar to dendritic cells' functions. In conclusion, our study demonstrates that SMs, potentially crucial for immune activation, diminish in the LNs of elderly patients. This reduction of SMs may contribute to the immune dysfunction observed in the elderly.

Lymph nodes are secondary lymphoid organs localized throughout the body that typically appear as bean-like nodules. Numerous antigen-presenting cells, including dendritic cells and macrophages, that mediate host defense responses against pathogens, such as bacteria and viruses, reside within lymph nodes. To react to cancer cell-derived antigens in a variety of cancers, antigen-presenting cells induce cytotoxic T lymphocytes (CTLs). In relation to anticancer immune responses, macrophages in the lymph node sinus have been of particular interest because a number of studies involving both human specimens and animal models have reported that lymph node macrophages expressing CD169 play a key role in activating anticancer CTLs. Recent studies have indicated that dysfunction of lymph node macrophages potentially contributes to immune suppression in elderly patients and immunological "cold" tumors. Therefore, in anticancer therapy, the regulation of lymph node macrophages is a potentially promising approach.

The in vitro reconstruction assay enables us to evaluate in detail the insertion and proper protein folding (together termed assembly) of β-barrel membrane proteins. Here, we introduce an in vitro reconstitution experiments using isolated membrane fractions from Escherichia coli (E. coli). Membrane fractions isolated from E. coli cells and disrupted by sonication, which we have termed E. coli microsomal (mid-density) membrane (EMM), are ideal for biochemical experiments, as they can be harvested by high-speed centrifugation and do not require ultra-centrifugation. EMM pretreated with detergent can assemble externally supplemented β-barrel membrane proteins via intact β-barrel assembly machinery (BAM) complex retained in EMM. This method not only allows assembly analysis with inexpensive equipment but it also can be applied to drug screening using assembly as an indicator with high reproducibility. In this chapter, we introduce our method of evaluating assembled β-barrel membrane proteins by demonstrating four representative β-barrel membrane proteins: E. coli major porins OmpA and OmpF; enterohemorrhagic E. coli (EHEC) autotransporter EspP, and Haemophilus influenzae (H. influenzae) adhesin Hia., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Membrane vesicles (MVs) are small spherical structures (20-400 nm) produced by most bacteria and have important biological functions including toxin delivery, signal transfer, biofilm formation, and immunomodulation of the host. Although MV formation is enhanced in biofilms of a wide range of bacterial species, the underlying mechanisms are not fully understood. An opportunistic pathogen, Pseudomonas aeruginosa , causes chronic infections that can be difficult to treat due to biofilm formation. Since MVs are abundant in biofilms, can transport virulence factors to the host, and have inflammation-inducing functions, the mechanisms of enhanced MV formation in biofilms needs to be elucidated to effectively treat infections. In this study, we evaluated the characteristics of MVs in P. aeruginosa PAO1 biofilms, and identified factors that contribute to enhanced MV formation. Vesiculation was significantly enhanced in the static culture; MVs were connected to filamentous substances in the biofilm, and separation between the outer and inner membranes and curvature of the membrane were observed in biofilm cells. By screening a transposon mutant library (8,023 mutants) for alterations in MV formation in biofilms, 66 mutants were identified as low-vesiculation strains (2/3 decrease relative to wild type), whereas no mutant was obtained that produced more MVs (twofold increase). Some transposons were inserted into genes related to biofilm formation, including flagellar motility ( flg , fli , and mot ) and extracellular polysaccharide synthesis ( psl ). Δ pelA Δ pslA , which does not synthesize the extracellular polysaccharides Pel and Psl, showed reduced MV production in biofilms but not in planktonic conditions, suggesting that enhanced vesiculation is closely related to the synthesis of biofilm matrices in P. aeruginosa . Additionally, we found that blebbing occurred during bacterial attachment. Our findings indicate that biofilm-related factors are closely involved in enhanced MV formation in biofilms and that surface sensing facilitates vesiculation. Furthermore, this work expands the understanding of the infection strategy in P. aeruginosa biofilms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Kanno, Shiota, Ueno, Takahara, Haneda, Tahara, Shintani, Nakao, Miyata, Kimbara, Futamata and Tashiro.)