No abstract

Degradation of the endoplasmic reticulum (ER) via selective autophagy (ER‐phagy) is vital for cellular homeostasis. We identify FAM134A/RETREG2 and FAM134C/RETREG3 as ER‐phagy receptors, which predominantly exist in an inactive state under basal conditions. Upon autophagy induction and ER stress signal, they can induce significant ER fragmentation and subsequent lysosomal degradation. FAM134A, FAM134B/RETREG1, and FAM134C are essential for maintaining ER morphology in a LC3‐interacting region (LIR)‐dependent manner. Overexpression of any FAM134 paralogue has the capacity to significantly augment the general ER‐phagy flux upon starvation or ER‐stress. Global proteomic analysis of FAM134 overexpressing and knockout cell lines reveals several protein clusters that are distinctly regulated by each of the FAM134 paralogues as well as a cluster of commonly regulated ER‐resident proteins. Utilizing pro‐Collagen I, as a shared ER‐phagy substrate, we observe that FAM134A acts in a LIR‐independent manner and compensates for the loss of FAM134B and FAM134C, respectively. FAM134C instead is unable to compensate for the loss of its paralogues. Taken together, our data show that FAM134 paralogues contribute to common and unique ER‐phagy pathways.

Central nervous system (CNS) delivery of anti-inflammatory cytokines, such as interleukin 4 (IL4), holds promise as treatment for multiple sclerosis (MS). We have previously shown that short-term herpes simplex virus type 1-mediated IL4 gene therapy is able to inhibit experimental autoimmune encephalomyelitis (EAE), an animal model of MS, in mice and non-human primates. Here, we show that a single administration of an IL4-expressing helper-dependent adenoviral vector (HD-Ad) into the cerebrospinal fluid (CSF) circulation of immunocompetent mice allows persistent transduction of neuroepithelial cells and long-term (up to 5 months) CNS transgene expression without toxicity.Mice affected by chronic and relapsing EAE display clinical and neurophysiological recovery from the disease once injected with the IL4-expressing HD-Ad vector. The therapeutic effect is due to the ability of IL4 to increase, in inflamed CNS areas, chemokines (CCL1, CCL17 and CCL22) capable of recruiting regulatory T cells (CD4 + CD69 À CD25 + Foxp3 + ) with suppressant functions. CSF delivery of HD-Ad vectors expressing anti-inflammatory molecules might represent a valuable therapeutic option for CNS inflammatory disorders.

No abstract

Stem cells are currently seen as a treatment for tissue regeneration in neurological diseases such as multiple sclerosis, anticipating that they integrate and differentiate into neural cells. Mesenchymal stem cells (MSCs), a subset of adult progenitor cells, differentiate into cells of the mesodermal lineage but also, under certain experimental circumstances, into cells of the neuronal and glial lineage. Their clinical development, however, has been significantly boosted by the demonstration that MSCs display significant therapeutic plasticity mainly occurring through bystander mechanisms. These features have been exploited in the effective treatment of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis where the inhibition of the autoimmune response resulted in a significant amelioration of disease and decrease of demyelination, immune infiltrates and axonal loss. Surprisingly, these effects do not require MSCs to engraft in the central nervous system but depend on the cells' ability to inhibit pathogenic immune responses both in the periphery and inside the central nervous system and to release neuroprotective and pro-oligodendrogenic molecules favoring tissue repair. These results paved the road for the utilization of MSCs for the treatment of multiple sclerosis.

CD4+Foxp3+ regulatory T cells (Tregs) have been considered crucial in controlling immune system homeostasis, and their derangement is often associated to autoimmunity. Tregs identification is, however, difficult because most markers, including CD25 and Foxp3, are shared by recently activated T cells. We show in this paper that CD4+Foxp3+ T cells are generated in peripheral lymphoid organs on immunization and readily accumulate in the target organ of an autoimmune reaction, together with classical inflammatory cells, constituting up to 50% of infiltrating CD4+ T cells. Most CD4+Foxp3+ T cells are, however, CD25− and express proinflammatory cytokines such as IL-17 and IFN-γ, questioning their suppressive nature. Moreover, in vitro CD4+ T lymphocytes from naive and autoimmune mice, stimulated to differentiate into Th1, Th2, Th17, and induced Tregs, display early mixed expression of lineage-specific markers. These results clearly point to an unprecedented plasticity of naive CD4+ T cells, that integrating inflammatory signals may change their fate from the initial lineage commitment to a different functional phenotype.

No abstract

In the tumor microenvironment, cancer cells experience hypoxia resulting in the accumulation of misfolded/unfolded proteins largely in the endoplasmic reticulum (ER). Consequently, ER proteotoxicity elicits unfolded protein response (UPR) as an adaptive mechanism to resolve ER stress. In addition to canonical UPR, proteotoxicity also stimulates the selective, autophagy-dependent, removal of discrete ER domains loaded with misfolded proteins to further alleviate ER stress. These mechanisms can favor cancer cell growth, metastasis, and long-term survival. Our investigations reveal that during hypoxia-induced ER stress, the ER-phagy receptor FAM134B targets damaged portions of ER into autophagosomes to restore ER homeostasis in cancer cells. Loss of FAM134B in breast cancer cells results in increased ER stress and reduced cell proliferation. Mechanistically, upon sensing hypoxia-induced proteotoxic stress, the ER chaperone BiP forms a complex with FAM134B and promotes ER-phagy. To prove the translational implication of our mechanistic findings, we identified vitexin as a pharmacological agent that disrupts FAM134B-BiP complex, inhibits ER-phagy, and potently suppresses breast cancer progression in vivo.