NE/β2-AR Promotes Directional Migration of Colorectal Cancer Cells to the Liver by Inducing M2 Polarization of Kupffer Cells and Upregulating CXCL12 Expression

Background and Aim The exact mechanism of colorectal cancer (CRC) liver metastasis remains unclear. This study aimed to explore the role and mechanism of the norepinephrine (NE) in the directional migration of CRC cells to the liver.Methods In mouse models of CRC liver metastasis, the effects of NE on the number of liver metastases and the density of intrahepatic Kupffer cells (KCs) were observed. In vitro experiments were performed to detect KC polarization markers by flow cytometry, cytokines by enzyme-linked immunosorbent assay (ELISA), migration of colon cancer cells by Transwell migration assay, AR expression and PI3K/Akt signaling pathway-related protein expressions by Western blotting, and chemokine mRNA expressions by reverse transcription-polymerase chain reaction (RT-PCR).Results Two weeks after intraperitoneal injection of different doses of NE in CRC liver metastasis mouse models, the number of liver metastases were (111.00±51.43) and (102.40±54.85) in the low-dose (0.28 nmol) NE group and high-dose groups (2.8 nmol), respectively, which were significantly higher than those in the control group (both P＜0.05); in addition, the density of intrahepatic KCs in the NE group was significantly reduced compared with the control group (P<0.05). In vitro experiments showed that low-concentration NE induced M2 polarization of KCs; NE upregulated the expression level of NE receptor β2-AR on KCs and activated the PI3K/Akt pathway, while blocking β2-AR or using a PI3K inhibitor inhibited this process (P< 0.05). M2 KCs promoted the migration of colon cancer cell line CT26. Eight macrophage-associated chemokines were screened from the TISIDB website. CXCL12 expression in KCs was significantly higher in low-concentration (10-9 M) NE group than in controls, and a β2-AR blocker down-regulated CXCL12 expression in KCs (both P < 0.05).Conclusions NE/β2-AR may induce intrahepatic KC M2 polarization through the PI3K/Akt pathway and promote its secretion of CXCL12 to induce the directional migration of CRC to the liver. Our findings provide important evidence in the search for new strategies to prevent liver metastasis from CRC.

A self-generated Toddler gradient guides mesodermal cell migration

The sculpting of germ layers during gastrulation relies on coordinated migration of progenitor cells, yet the cues controlling these long-range directed movements remain largely unknown. While directional migration often relies on a chemokine gradient generated from a localized source, we find that zebrafish ventrolateral mesoderm is guided by the uniformly expressed and secreted protein Toddler/ELABELA/Apela, acting as a self-generated gradient. We show that the Apelin receptor, which is specifically expressed in mesodermal cells, has a dual role during gastrulation, acting as a scavenger receptor to generate a Toddler gradient, and as a chemokine receptor to sense this guidance cue. Thus, we uncover a single receptor-based self-generated gradient as the enigmatic guidance cue that can robustly steer the directional migration of mesoderm through the complex and continuously changing environment of the gastrulating embryo.

TNF-α-mediated m6A modification of ELMO1 triggers directional migration of mesenchymal stem cell in ankylosing spondylitis

Ankylosing spondylitis (AS) is a type of rheumatic disease characterized by chronic inflammation and pathological osteogenesis in the entheses. Previously, we demonstrated that enhanced osteogenic differentiation of MSC from AS patients (AS-MSC) resulted in pathological osteogenesis, and that during the enhanced osteogenic differentiation course, AS-MSC induced TNF-α-mediated local inflammation. However, whether TNF-α in turn affects AS-MSC remains unknown. Herein, we further demonstrate that a high-concentration TNF-α treatment triggers enhanced directional migration of AS-MSC in vitro and in vivo, which enforces AS pathogenesis. Mechanistically, TNF-α leads to increased expression of ELMO1 in AS-MSC, which is mediated by a METTL14 dependent m6A modification in ELMO1 3′UTR. Higher ELMO1 expression of AS-MSC is found in vivo in AS patients, and inhibiting ELMO1 in SKG mice produces therapeutic effects in this spondyloarthritis model. This study may provide insight into not only the pathogenesis but also clinical therapy for AS.

MTCL2 promotes asymmetric microtubule organization by crosslinking microtubules on the Golgi membrane

The Golgi complex plays an active role in organizing asymmetric microtubule arrays essential for polarized vesicle transport. The coiled-coil protein MTCL1 stabilizes microtubules nucleated from the Golgi membrane. Here, we report an MTCL1 paralog, MTCL2, which preferentially acts on the perinuclear microtubules accumulated around the Golgi. MTCL2 associates with the Golgi membrane through the N-terminal coiled-coil region and directly binds microtubules through the conserved C-terminal domain without promoting microtubule stabilization. Knockdown of MTCL2 significantly impaired microtubule accumulation around the Golgi as well as the compactness of the Golgi ribbon assembly structure. Given that MTCL2 forms parallel oligomers through homo-interaction of the central coiled-coil motifs, our results indicate that MTCL2 promotes asymmetric microtubule organization by crosslinking microtubules on the Golgi membrane. Results of in vitro wound healing assays further suggest that this function of MTCL2 enables integration of the centrosomal and Golgi-associated microtubules on the Golgi membrane, supporting directional migration. Additionally, the results demonstrated the involvement of CLASPs and giantin in mediating the Golgi association of MTCL2.

GSK3 as a Regulator of Cytoskeleton Architecture: Consequences for Health and Disease

Glycogen synthase kinase 3 (GSK3) was initially isolated as a critical protein in energy metabolism. However, subsequent studies indicate that GSK-3 is a multi-tasking kinase that links numerous signaling pathways in a cell and plays a vital role in the regulation of many aspects of cellular physiology. As a regulator of actin and tubulin cytoskeleton, GSK3 influences processes of cell polarization, interaction with the extracellular matrix, and directional migration of cells and their organelles during the growth and development of an animal organism. In this review, the roles of GSK3–cytoskeleton interactions in brain development and pathology, migration of healthy and cancer cells, and in cellular trafficking of mitochondria will be discussed.

Dynamic Rearrangement and Directional Migration of Tubular Vacuoles are Required for the Asymmetric Division of the Arabidopsis Zygote

In most flowering plants, asymmetric cell division of zygotes is the initial step to establish the apical–basal axis. In the Arabidopsis zygote, vacuolar accumulation at the basal cell end is crucial to ensure zygotic division asymmetry. Despite the importance, it was unclear whether this polar vacuolar distribution is achieved by predominant biogenesis at the basal region or by directional movement after biogenesis. Here, we found that apical and basal vacuolar contents are dynamically exchanged via tubular vacuolar network and the vacuoles gradually migrate towards the basal end. The mutant of a vacuolar membrane protein, SHOOT GRAVITROPISM2 (SGR2), failed to form tubular vacuoles, and the mutant of a putative vacuolar fusion factor, VESICLE TRANSPORT THROUGH INTERACTION WITH T-SNARES11 (VTI11), could not flexibly rearrange the vacuolar network. Both mutants failed to exchange the apical and basal vacuolar contents and to polarly migrate the vacuoles, resulting in more symmetric division of zygotes. Additionally, we observed that in contrast to sgr2, the zygotic defects of vti11 were rescued by the pharmacological depletion of phosphatidylinositol 3-phosphate (PI3P), a distinct phospholipid in the vacuolar membrane. Thus, SGR2 and VTI11 have individual sites of action in the zygotic vacuolar membrane processes. Further, a mutant of YODA (YDA) MAPKK kinase, a core component of the embryonic axis formation pathway, generated proper vacuolar network; however, it failed to migrate the vacuoles towards the basal region, which suggests impaired directional cues. Overall, we conclude that SGR2- and VTI11-dependent vacuolar exchange and YDA-mediated directional migration are necessary to achieve polar vacuolar distribution in the zygote.

Contractility, focal adhesion orientation, and stress fiber orientation drive cancer cell polarity and migration along wavy ECM substrates

Contact guidance is a powerful topographical cue that induces persistent directional cell migration. Healthy tissue stroma is characterized by a meshwork of wavy extracellular matrix (ECM) fiber bundles, whereas metastasis-prone stroma exhibit less wavy, more linear fibers. The latter topography correlates with poor prognosis, whereas more wavy bundles correlate with benign tumors. We designed nanotopographic ECM-coated substrates that mimic collagen fibril waveforms seen in tumors and healthy tissues to determine how these nanotopographies may regulate cancer cell polarization and migration machineries. Cell polarization and directional migration were inhibited by fibril-like wave substrates above a threshold amplitude. Although polarity signals and actin nucleation factors were required for polarization and migration on low-amplitude wave substrates, they did not localize to cell leading edges. Instead, these factors localized to wave peaks, creating multiple “cryptic leading edges” within cells. On high-amplitude wave substrates, retrograde flow from large cryptic leading edges depolarized stress fibers and focal adhesions and inhibited cell migration. On low-amplitude wave substrates, actomyosin contractility overrode the small cryptic leading edges and drove stress fiber and focal adhesion orientation along the wave axis to mediate directional migration. Cancer cells of different intrinsic contractility depolarized at different wave amplitudes, and cell polarization response to wavy substrates could be tuned by manipulating contractility. We propose that ECM fibril waveforms with sufficiently high amplitude around tumors may serve as “cell polarization barriers,” decreasing directional migration of tumor cells, which could be overcome by up-regulation of tumor cell contractility.