Tripartite Motif Family Research Articles

TRIM24 protein promotes and TRIM32 protein inhibits cardiomyocyte hypertrophy via regulation of dysbindin protein levels

We have previously shown that dysbindin is a potent inducer of cardiomyocyte hypertrophy via activation of Rho-dependent serum-response factor (SRF) signaling. We have now performed a yeast two-hybrid screen using dysbindin as bait against a cardiac cDNA library to identify the cardiac dysbindin interactome. Among several putative binding proteins, we identified tripartite motif-containing protein 24 (TRIM24) and confirmed this interaction by co-immunoprecipitation and co-immunostaining. Another tripartite motif (TRIM) family protein, TRIM32, has been reported earlier as an E3 ubiquitin ligase for dysbindin in skeletal muscle. Consistently, we found that TRIM32 also degraded dysbindin in neonatal rat ventricular cardiomyocytes as well. Surprisingly, however, TRIM24 did not promote dysbindin decay but rather protected dysbindin against degradation by TRIM32. Correspondingly, TRIM32 attenuated the activation of SRF signaling and hypertrophy due to dysbindin, whereas TRIM24 promoted these effects in neonatal rat ventricular cardiomyocytes. This study also implies that TRIM32 is a key regulator of cell viability and apoptosis in cardiomyocytes via simultaneous activation of p53 and caspase-3/-7 and inhibition of X-linked inhibitor of apoptosis. In conclusion, we provide here a novel mechanism of post-translational regulation of dysbindin and hypertrophy via TRIM24 and TRIM32 and show the importance of TRIM32 in cardiomyocyte apoptosis in vitro.

TRIM59 is a key regulator of growth and migration inrenal cell carcinoma.

Renal cell carcinoma (RCC) is the most common renal neoplasms and metastatic is common. Previous data have shown that the tripartite motif (TRIM) family proteinswere implicated in human tumoriogenesis. In this study, we aimed to investigate the role of TRIM59 in the cell growth and migration in RCC. The expression of TRIM59 in human RCC tissues was initially examined by qRT-PCR. Alentivirus-based shRNA against TRIM59 (Lv-shTRIM59) was constructed. The effects of TRIM59 knockdown on cell proliferation were examined by in vitro MTT assay, colony formation assay and in vivo a mouse xenograft model of RCC. Cell migration and invasion after knockdown of TRIM59 were also examined by transwell assay. Our data showed that the mRNA level of TRIM59 in cancerous tissues was 2-fold increased as compared with non-cancerous tissues. Knockdown of TRIM59 in a RCC cell line 786-O significantly slowed down cell proliferative rate and decreased both the colony number and sizes. In the mouse model, knockdown of TRIM59 consistently inhibited tumor growth in vivo. Moreover, it was shown that cell migration and invasion were suppressed by 68% and 50%, respectively in TRIM59-depleted 786-O cells. Our data suggest that TRIM59 may serve as a pro-oncogenic protein in promoting the progression of RCC. Knockdown of TRIM59 may be a promising strategy concerning the early detection and treatment of RCC.

Knockdown of Tripartite-59 (TRIM59) Inhibits Cellular Proliferation and Migration in Human Cervical Cancer Cells.

The tripartite motif (TRIM) family of proteins is a class of highly conservative proteins that have been implicated in multiple processes. TRIM59, one member of the TRIM family, has now received recognition as a key regulator in the development and progression of human diseases. However, its role in human tumorigenesis has remained largely unknown. In this study, the effects of TRIM59 expression on cell proliferation and migration were investigated in human cervical cancer cells. The expression of TRIM59 in clinical cervical cancer tissues and cervical cancer cells was initially determined by RT-PCR and Western blot. Specific shRNA against TRIM59 was then employed to knock down the expression of TRIM59 in cervical cancer lines HeLa and SiHa. The effects of TRIM59 knockdown on cell proliferation was assessed by MTT assay and colony formation assay. Transwell assay was conducted to reveal cell migration and invasion abilities before and after TRIM59 knockdown. Our results showed that the expression of TRIM59 was significantly elevated in cervical cancers. Knockdown of TRIM59 significantly inhibited cell proliferation and colony formation as well as cell migration and invasion abilities in cervical cancer HeLa and SiHa cells. Cell cycle progression analysis showed that TRIM59-depleted cells preferred to accumulate in the S phase. These data suggest that TRIM59 is a potential target that promotes the progression of cervical cancer.

Expression profiling of TRIM protein family in THP1-derived macrophages following TLR stimulation

Activated macrophages play an important role in many inflammatory diseases including septic shock and atherosclerosis. However, the molecular mechanisms limiting macrophage activation are not completely understood. Members of the tripartite motif (TRIM) family have recently emerged as important players in innate immunity and antivirus. Here, we systematically analyzed mRNA expressions of representative TRIM molecules in human THP1-derived macrophages activated by different toll-like receptor (TLR) ligands. Twenty-nine TRIM members were highly induced (>3 fold) by one or more TLR ligands, among which 19 of them belong to TRIM C-IV subgroup. Besides TRIM21, TRIM22 and TRIM38 were shown to be upregulated by TLR3 and TLR4 ligands as previous reported, we identified a novel group of TRIM genes (TRIM14, 15, 31, 34, 43, 48, 49, 51 and 61) that were significantly up-regulated by TLR3 and TLR4 ligands. In contrast, the expression of TRIM59 was down-regulated by TLR3 and TLR4 ligands in both human and mouse macrophages. The alternations of the TRIM proteins were confirmed by Western blot. Finally, overexpression of TRIM59 significantly suppressed LPS-induced macrophage activation, whereas siRNA-mediated knockdown of TRIM59 enhanced LPS-induced macrophage activation. Taken together, the study provided an insight into the TLR ligands-induced expressions of TRIM family in macrophages.

Structural determinants of TRIM protein function.

Tripartite motif (TRIM) proteins constitute one of the largest subfamilies of Really Interesting New Gene (RING) E3 ubiquitin ligases and contribute to the regulation of numerous cellular activities, including innate immune responses. The conserved TRIM harbours a RING domain that imparts E3 ligase activity to TRIM family proteins, whilst a variable C-terminal region can mediate recognition of substrate proteins. The knowledge of the structure of these multidomain proteins and the functional interplay between their constituent domains is paramount to understanding their cellular roles. To date, available structural information on TRIM proteins is still largely restricted to subdomains of many TRIMs in isolation. Nevertheless, applying a combination of structural, biophysical and biochemical approaches has recently allowed important progress to be made towards providing a better understanding of the molecular features that underlie the function of TRIM family proteins and has uncovered an unexpected diversity in the link between self-association and catalytic activity.

TRIM Family Proteins in Intracellular Vesicle Trafficking

The tripartite motif (TRIM) family of over 75 different proteins serves regulative roles in many critical aspects of health and disease including wound healing, immunity, secretion and cancer. Our laboratory has previously shown that MG53 (TRIM72) played an essential role in cell membrane repair via trafficking of intracellular vesicles to the injury site. TRIM50 is the closest homologue to MG53, however, it has dissimilar cellular function and tissue localization. The molecular mechanisms that underlie the different functions for MG53 and TRIM50 are unknown. An earlier study from our group showed that TRIM50 is predominantly expressed in the stomach, and is involved in vesicle trafficking during acid secretion in gastric parietal cells. While we know that MG53-mediated vesicle translocation to membrane injury site is driven by a molecular motor named non-muscle myosin II-A (NM2A), the molecular motor that facilitates TRIM50 movement during acid secretion is unknown. In this study, we used intracellular vesicle tracking to examine how TRIM50-associated vesicles move within the cell, distinguishing between diffusive and directional ballistic motions. We found that gastric carcinoma TMK-1 cells transfected with mCherry-TRIM50 display non-diffusive movements, and treatment with microtubule inhibitors such as nocodazole and colchicine abolished the directed motion of the TRIM50-associated vesicles. To determine the differential function and cytoskeletal associations of MG53 and TRIM50, chimeric proteins were constructed and tested for response to cell membrane injury, preferential lipid binding (e.g. phosphatidylserine for MG53 vs phosphatidylinositol for TRIM50), and subcellular localization. Overall, our data suggest that TRIM50-vesicles are associated with dynein, a microtubule-associated molecular motor, to power vesicle trafficking related to acid secretion in gastric parietal cells. Additionally, the critical regions responsible for the differential functions of MG53 and TRIM50 was not found within the divergent C-terminal PRY/SPRY domain, as we had predicted. This study suggests that the N-terminal domain of TRIM family proteins may be responsible for vesicle trafficking, providing a clue on how TRIM family proteins regulate vesicle trafficking and how the genetic ablation of TRIM50 is involved in the gastrointestinal symptoms observed in patients with Williams Syndrome. Additionally, it suggests that we could use a shorter form of MG53 as a new therapeutic agent for muscular dystrophy and cardiovascular disease.

MG53 Negatively Regulates NLRP3 to Inhibit Inflammation Associated with Tissue Injury

MG53 is a member of the tripartite motif family with E3 ubiquitin ligase activity, and plays important roles in cell membrane repair, tissue regeneration and wound healing. We previously showed that topical or systemic administration of recombinant human MG53 (rhMG53) protein protected against tissue injury and reduced the level of inflammatory cytokines (e.g. IL-1β) in circulation. NLRP3 is a key member of the inflammasome complex that mediates the cleavage and activation of caspase-1 for control of IL-1β release into circulation. As tissue injury is often associated with inflammation, we hypothesize that MG53 interacts with NLRP3 to control inflammasome signaling associated with tissue injury. With the mg53-/- mice, we found the spleen organ was significantly enlarged compared with the wild type littermates. The protein level of NLRP3 in the spleen was up-regulated in the mg53-/- mice. In cultured HEK293 cells, co-expression of MG53 with NLRP3 led to down-regulation of NLRP3 in a proteasome-dependent manner. Down-regulation of NLRP3 was not observed in cells co-transfected with a mutant MG53 lacking E3-ligase activity. Co-immunpprecipitation studies revealed a physical interaction between MG53 and NLRP3. With human monocytes (THP-1 cells) transfected with RFP-MG53 and GFP-NLRP3, we observed the trafficking of MG53 and NLRP3 associated with inflammasome formation. Upon treatment with LPS and ATP, THP-1 cells responded with formation of inflammasomes and co-segregation of NLRP3 and MG53. The level of NLRP3 in THP-1 cells co-expressing MG53 was significantly lower compared with cells do not express MG53. Together, these findings suggest that MG53 act as a negative regulator of NLRP3 to control inflammasome signaling. More in vivo studies are required to dissect the physiological role of MG53 in modulating the immune response associated with tissue injury.

Upregulated Expression of TRIM32 Is Involved in Schwann Cell Differentiation, Migration and Neurite Outgrowth After Sciatic Nerve Crush.

Tripartite motif containing 32 (TRIM32), a member of the tripartite motif (TRIM) family, plays an indispensable role in myoblast proliferation. It also regulates neuron and skeletal muscle stem cell differentiation. Although it is of great importance, we know little about the roles of TRIM32 during peripheral nervous system injury. Here, we examined the dynamic changes of TRIM32 in acute sciatic nerve crush (SNC) model. After crush, TRIM32 rapidly increased and reached the climax at 1week but then gradually declined to the normal level at 4weeks post-injury. Meanwhile, we observed similar changes of Oct-6. What is more, we found co-localization of TRIM32 with S100 and Oct-6 in 1-week-injured tissues using double immunofluorescent staining. In further vitro experiments, enhancive expression of TRIM32 was detected during the process of cyclic adenosine monophosphate (cAMP)-induced Schwann cell differentiation and nerve growth factor (NGF)-induced PC12 cell neurite outgrowth. More interestingly, specific si-TRIM32-transfected RSC96 cells exhibited obvious reduction in the ability of migration. Taken together, we inferred that upregulated TRIM32 was not only involved in the differentiation and migration of Schwann cells but the neurite elongation after SNC.

Macrophage production and activation are dependent on TRIM33.

The tripartite motif (TRIM) family of proteins plays important roles in innate immunity and antimicrobial infection. None of these proteins has been shown to directly regulate transcription of genes in monocyte/macrophage except TRIM33 that we have recently shown to be a macrophage specific transcriptional inhibitor of Ifnb1. Using ChIP-seq analyses, we now report that TRIM33 is bound to two fold more genes in immature than in mature myeloid cell lines. When located near the same genes, TRIM33 is bound to different sequences in the two cell lines suggesting a role of TRIM33 in both immature and mature myeloid cells. Accordingly, expression of TRIM33 in immature myeloid cells is necessary for efficient production of small peritoneal macrophages, monocytes and bone marrow derived macrophage (BMDM) and TRIM33 targets a subset of genes involved in the inflammatory response only in mature myeloid cells. Functionally, this targeting is associated with impaired repression of pathways regulating the late phases of lipopolysaccharide (LPS) activation of BMDM and a high sensitivity to LPS in vivo when the trim33 gene is inactivated in mature myeloid cells. These findings pinpoint TRIM33 as an important transcriptional actor of monocyte/macrophage mediated inflammation.

Molecular Characterization, Tissue Distribution and Expression, and Potential Antiviral Effects of TRIM32 in the Common Carp (Cyprinus carpio).

Tripartite motif-containing protein 32 (TRIM32) belongs to the tripartite motif (TRIM) family, which consists of a large number of proteins containing a RING (Really Interesting New Gene) domain, one or two B-box domains, and coiled coil motif followed by different C-terminal domains. The TRIM family is known to be implicated in multiple cellular functions, including antiviral activity. However, it is presently unknown whether TRIM32 of common carp (Cyprinus carpio) has the antiviral effect. In this study, the sequence, expression, and antiviral function of TRIM32 homolog from common carp were analyzed. The full-length coding sequence region of trim32 was cloned from common carp. The results showed that the expression of TRIM32 (mRNA) was highest in the brain, remained stably expressed during embryonic development, and significantly increased following spring viraemia of carp virus (SVCV) infection. Transient overexpression of TRIM32 in affected Epithelioma papulosum cyprinid cells led to significant decrease of SVCV production as compared to the control group. These results suggested a potentially important role of common carp TRIM32 in enhancing host immune response during SVCV infection both in vivo and in vitro.

The role of Trim25 in development, disease and RNA metabolism.

Trim25 is a member of the tripartite motif family of E3 ubiquitin ligases. It plays major roles in innate immunity and defence against viral infection, control of cell proliferation and migration of cancer cells. Recent work identified Trim25 as being able to bind to RNA and to regulate Lin28a-mediated uridylation of pre-let-7. Here we review the current knowledge of the role of Trim25 in development, disease and RNA metabolism.

Grouper TRIM13 exerts negative regulation of antiviral immune response against nodavirus.

The tripartite motif (TRIM)-containing proteins have attracted particular attention to their multiple functions in different biological processes. TRIM13, a member of the TRIM family, is a RING domain-containing E3 ubiquitin ligase which plays critical roles in diverse cellular processes including cell death, cancer and antiviral immunity. In this study, a TRIM13 homolog from orange spotted grouper, Epinephelus coioides (EcTRIM13) was cloned and characterized. The full-length of EcTRIM13 cDNA encoded a polypeptide of 399 amino acids which shared 81% identity with TRIM13 homolog from large yellow croaker (Larimichthys crocea). Amino acid alignment analysis showed that EcTRIM13 contained conserved RING finger and B-box domain. Expression patterns analysis indicated that EcTRIM13 was abundant in liver, spleen, kidney, intestine and gill. Moreover, the transcript of EcTRIM13 in grouper spleen was differently regulated after injection with Singapore grouper iridovirus (SGIV) or polyinosin-polycytidylic acid (poly I:C). Under fluorescence microscopy, we observed the tubular structure in wild type EcTRIM13 transfected cells, but the RING domain mutant resulted in the fluorescence distribution was changed and the bright punctate fluorescence was evenly situated throughout the cytoplasm, suggesting that the RING domain was essential for its accurate localization. Overexpression of EcTRIM13 in vitro obviously increased the replication of red spotted grouper nervous necrosis virus (RGNNV), and the enhancing effect of EcTRIM13 on virus replication was affected by the RING domain. Furthermore, the ectopic expression of EcTRIM13 not only negatively regulated the interferon promoter activity induced by interferon regulator factor (IRF) 3, IRF7, and melanoma differentiation-associated protein 5 (MDA5), but also decreased the expression of several interferon related factors. In addition, the overexpression of EcTRIM13 also differently regulated the transcription of pro-inflammatory factors. Together, our results firstly demonstrated that fish TRIM13 exerted negative regulation of antiviral response against nodavirus infection.

The role of PML in the activation and the differentiation of T cells and B cells

Abstract Promyelocytic leukemia protein (PML) is a tumor suppressor with diverse activities in cell growth, cell death, stress responses or senescence. PML is a member of the tripartite motif (TRIM) family protein, which contains RING, B-box and coiled-coil domains. Recent studies showed that large number of TRIM family proteins positively regulate innate immune signaling pathways by acting as E3 ubiquitin ligases. To investigate the role of PML in adaptive immunity, we examined the population of different T cell and B cell subsets in PML-knockout mice. The T cells population including CD4+, CD8+, CD25+, effector T, naïve T, and memory T cells were comparable between WT and PML-deficient mice. The B cells population including follicular B, transitional type 1 and 2 B cells, and marginal zone B cells were also comparable between WT and PML-knockout mice. We also determined whether the activation of T cells and B cells were affected by PML-deficiency. It was found that the activation of PML-deficient T and B cells was lower than that of WT cells. We further determined the differentiation of induced regulatory T (iTreg) cells, and observed that iTreg differentiation was comparable in WT and PML-deficient cells. Therefore, PML is not apparently involved in the development of T cells and B cells, and is modesty required for the full activation of T lymphocyte and B lymphocytes. The exact contribution of PML to the activation of T cell and B cell awaits further investigation.

Molecular Reproduction & Development Volume 83, Issue 5, May 2016

Zebrafi sh are particularly amenable to studying developmental processes due to their malleable genetics, rapid reproduction, in vitro fertilization, and the clarity of their embryos. These animals are also amenable to many technologies that allow for knockdown and overexpression studies. For example, Han et al. (this issue) describe identify the contributions of a novel tripartite motif family member, trim69, to p53‐mediated apoptosis using classic morpholino knockdown and mRNA overexpression analysis.

A novel TRIM family member, Trim69, regulates zebrafish development through p53-mediated apoptosis.

Trim69 contains the hallmark domains of a tripartite motif (TRIM) protein, including a Ring-finger domain, B-box domain, and coiled-coil domain. Trim69 is structurally and evolutionarily conserved in zebrafish, mouse, rat, human, and chimpanzee. The role of this protein is unclear, however, so we investigated its function in zebrafish development. Trim69 is extensively expressed in zebrafish adults and developing embryos-particularly in the testis, brain, ovary, and heart-and its expression decreases in a time- and stage-dependent manner. Loss of trim69 in zebrafish induces apoptosis and activates apoptosis-related processes; indeed, the tp53 pathway was up-regulated in response to the knockdown. Expression of human trim69 rescued the apoptotic phenotype, while overexpression of trim69 does not increase cellular apoptosis. Taken together, our results suggest that trim69 participates in tp53-mediated apoptosis during zebrafish development. Mol. Reprod. Dev. 83: 442-454, 2016. © 2016 Wiley Periodicals, Inc.

Trim33/Tif1γ is involved in late stages of granulomonopoiesis in mice.

Trim33/Tif1γ (Trim33) is a member of the tripartite motif family. Using a conditional hematopoietic-specific Trim33 knock-out (Trim33(Δ/Δ)) mouse, we showed previously that Trim33 deficiency in hematopoietic stem cells leads to severe defects in hematopoiesis, resembling the main features of human chronic myelomonocytic leukemia. We also demonstrated that Trim33 is involved in hematopoietic aging through TGFβ signaling. Nevertheless, how Trim33 contributes to the terminal stages of myeloid differentiation remainsto be clarified. We reveal here the crucial role of Trim33 expression in the control of mature granulomonocytic differentiation. An important component of Trim33-deficient mice is the alteration of myeloid differentiation, as characterized by dysplastic features, abnormal granulocyte and monocyte maturation, and the expansion of CD11b(+)Ly6G(high)Ly6C(low) myeloid cells, which share some features with polymorphonuclear-myeloid-derived suppressor cells. Moreover, in Trim33(Δ/Δ) mice, we observed the alteration of CSF-1-mediated macrophage differentiation in association with the lack of Csf-1 receptor.Altogether, these results indicate that Trim33 deficiency leads to the expansion of a subset of myeloid cells characterizing the myelodysplastic/myeloproliferative neoplasm.

TRIM59 is upregulated and promotes cell proliferation and migration in human osteosarcoma.

Osteosarcoma is a prevalent type of cancer and has a high metastatic ability, particularly for metastasis to the lungs. Effective treatment strategies have improved, however, the detailed molecular mechanism underlying the onset of this malignancy remains to be fully elucidated. The current study investigated the role of the tripartite motif (TRIM) family protein TRIM59 in osteosarcoma growth and metastasis. It was identified that TRIM59 was overexpressed in clinical osteosarcoma tissues and cultured osteosarcoma cell lines. In addition, the MTT assay demonstrated that in U2OS and MG63 cells, knockdown of TRIM59 by specific siRNA inhibited proliferation, whereas overexpression of TRIM59 promoted cell proliferation. Furthermore, overexpression of TRIM59 significantly increased the U2OS cell migrative and invasive abilities in a Transwell chamber assay. In addition, TRIM59 was able to negatively regulate the protein levels of P53 without significantly affecting the mRNA levels in U2OS and MG63cells. These data suggest the oncogenic abilities of TRIM59 in osteosarcoma, which promote osteosarcoma cell proliferation, migration and invasion.

The interferon-induced antiviral protein PML (TRIM19) promotes the restriction and transcriptional silencing of lentiviruses in a context-specific, isoform-specific fashion.

BackgroundThe promyelocytic leukemia (PML) protein, a type I interferon (IFN-I)-induced gene product and a member of the tripartite motif (TRIM) family, modulates the transcriptional activity of viruses belonging to various families. Whether PML has an impact on the replication of HIV-1 has not been fully addressed, but recent studies point to its possible involvement in the restriction of HIV-1 in human cells and in the maintenance of transcriptional latency in human cell lines in which HIV-1 is constitutively repressed. We investigated further the restriction of HIV-1 and a related lentivirus, SIVmac, by PML in murine cells and in a lymphocytic human cell line. In particular, we studied the relevance of PML to IFN-I-mediated inhibition and the role of individual human isoforms.ResultsWe demonstrate that both human PML (hPML) and murine PML (mPML) inhibit the early post-entry stages of the replication of HIV-1 and a related lentivirus, SIVmac. In addition, HIV-1 was transcriptionally silenced by mPML and by hPML isoforms I, II, IV and VI in MEFs. This PML-mediated transcriptional repression was attenuated in presence of the histone deacetylase inhibitor SAHA. In contrast, depletion of PML had no effect on HIV-1 gene expression in a human T cell line. PML was found to contribute to the inhibition of HIV-1 by IFN-I. Specifically, IFN-α and IFN-β treatments of MEFs enhanced the PML-dependent inhibition of HIV-1 early replication stages.ConclusionsWe show that PML can inhibit HIV-1 and other lentiviruses as part of the IFN-I-mediated response. The restriction takes place at two distinct steps, i.e. reverse transcription and transcription, and in an isoform-specific, cellular context-specific fashion. Our results support a model in which PML activates innate immune antilentiviral effectors. These data are relevant to the development of latency reversal-inducing pharmacological agents, since PML was previously proposed as a pharmacological target for such inhibitors. This study also has implications for the development of murine models of HIV-1.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-016-0253-1) contains supplementary material, which is available to authorized users.

Zinc Binding to MG53 Facilitates Repair of Injury to Cell Membrane

Zinc (Zn) is an essential trace element that participates in a wide range of biological functions, including wound healing. While Zn deficiency has been linked to compromised wound healing and tissue repair in human diseases, the molecular mechanisms underlying Zn-mediated tissue repair remain unknown. Our previous studies established that MG53, a tripartite motif (TRIM) family protein, is an essential component of the cell membrane repair machinery. Domain homology analysis reveals that MG53 contains two Zn-binding motifs. Here we show that Zn-binding to MG53 is indispensible to the assembly of the cell membrane repair machinery. Live cell imaging illustrates that Zn entry from extracellular space is essential for translocation of MG53-containing vesicles to the acute membrane injury sites for formation of a repair patch. The effect of Zn on membrane repair is abolished in the mg53-/- muscle fibers, suggesting that MG53 functions as a potential target for Zn during membrane repair. Mutagenesis studies suggest that both RING and B-box motifs of MG53 constitute Zn-binding domains that contribute to MG53-mediated membrane repair. Overall, this study establishes a base for Zn interaction with MG53 in protection against injury to the cell membrane.

MG53 Promotes Wound Healing and Reduces Scar Formation by Facilitating Cell Membrane Repair and Controlling Myofibroblast Differentiation

Cell membrane repair is an important aspect of physiology, and disruption of this process can result in pathophysiology in a number of different tissues including wound healing, chronic ulcer and scaring. We previously identified a novel TRIM (tripartite-motif) family protein, named MG53, as an essential component of the cell membrane repair machinery. Here we report the functional role of MG53 in modulation of wound healing and scarring. Although MG53 is absent from keratinocytes and fibroblasts, remarkable defects in skin architecture and collagen over-production are observed in mg53-/- mice; and these animals display delayed wound healing and abnormal scarring. Recombinant human MG53 (rhMG53) protein, encapsulated in hydrogel formulation, facilitates wound healing and prevents scarring in rodent models of dermal injuries. In vitro study shows that rhMG53 protects against acute injury to keratinocytes and facilitates migration of fibroblasts in response to scratch wounding. During fibrotic remodeling, rhMG53 interferes with TGF-β-dependent activation of myofibroblast differentiation; the resulting down-regulation of alpha smooth muscle actin (α-SMA) and extracellular matrix proteins contributes to reduced scarring. Overall, these studies establish a tri-functional role for MG53 as a facilitator of rapid injury repair, a mediator of cell migration, and a modulator of myofibroblast differentiation during wound healing. Targeting the functional interaction between MG53 and TGF-β signaling may present a potentially effective means for promoting scarless wound healing.