Modulating Chaperone-Mediated Autophagy and Its Clinical Applications in Cancer.

Autophagy is a central mechanism for maintaining cellular homeostasis in health and disease as it provides the critical energy through the breakdown and recycling of cellular components and molecules within lysosomes. One of the three types of autophagy is chaperone-mediated autophagy (CMA), a degradation pathway selective for soluble cytosolic proteins that contain a targeting motif related to KFERQ in their amino acid sequence. This motif marks them as CMA substrate and is, in the initial step of CMA, recognised by the heat shock protein 70 (Hsc70). The protein complex is then targeted to the lysosomal membrane where the interaction with the splice variant A of the lysosomal-associated membrane protein-2 (LAMP-2A) results in its unfolding and translocation into the lysosome for degradation. Altered levels of CMA have been reported in a wide range of pathologies including many cancer types that upregulate CMA as part of the pro-tumorigenic phenotype, while in aging a decline is observed and associated with a decrease of LAMP-2 expression. The potential of altering CMA to modify a physiological or pathological process has been firmly established through genetic manipulation in animals and chemical interference with this pathway. However, its use for therapeutic purposes has remained limited. Compounds used to target and modify CMA have been applied successfully to gain a better understanding of its cellular mechanisms, but they are mostly not specific, also influence other autophagic pathways and are associated with high levels of toxicity. Here, we will focus on the molecular mechanisms involved in CMA regulation as well as on potential ways to intersect them, describe modulators successfully used, their mechanism of action and therapeutic potential. Furthermore, we will discuss the potential benefits and drawbacks of CMA modulation in diseases such as cancer.

A Novel Role for GATA3 in Mesangial Cells in Glomerular Development and Injury.

BACKGROUND: GATA3 is a dual-zinc finger transcription factor that regulates gene expression in many developing tissues. In the kidney, GATA3 is essential for ureteric bud branching, and mice without it fail to develop kidneys. In humans, autosomal dominant GATA3 mutations can cause renal aplasia as part of the hypoparathyroidism, renal dysplasia, deafness (HDR) syndrome that includes mesangioproliferative GN. This suggests that GATA3 may have a previously unrecognized role in glomerular development or injury. METHODS: To determine GATA3's role in glomerular development or injury, we assessed GATA3 expression in developing and mature kidneys from Gata3 heterozygous (+/-) knockout mice, as well as injured human and rodent kidneys. RESULTS: We show that GATA3 is expressed by FOXD1 lineage stromal progenitor cells, and a subset of these cells mature into mesangial cells (MCs) that continue to express GATA3 in adult kidneys. In mice, we uncover that GATA3 is essential for normal glomerular development, and mice with haploinsufficiency of Gata3 have too few MC precursors and glomerular abnormalities. Expression of GATA3 is maintained in MCs of adult kidneys and is markedly increased in rodent models of mesangioproliferative GN and in IgA nephropathy, suggesting that GATA3 plays a critical role in the maintenance of glomerular homeostasis. CONCLUSIONS: These results provide new insights on the role GATA3 plays in MC development and response to injury. It also shows that GATA3 may be a novel and robust nuclear marker for identifying MCs in tissue sections.

Heterogeneity of macrophage activation in anti-Thy-1.1 nephritis.

Macrophages infiltrating glomeruli in telescoped nephrotoxic nephritis are programmed. The purpose of this study was to assess whether macrophages infiltrating glomeruli of rats with passively induced injury become similarly programmed, and to determine whether macrophage commitment is an early event. Glomerular macrophages isolated from rats with resolving and proliferative anti-Thy-1 nephritis were examined for nitric oxide (NO) generation and expression of lysosomal hydrolases. After a single injection of Thy-1 antibody the cells generated large amounts of NO that was attenuated ex vivo by transforming growth factor-beta and other anti-inflammatory cytokines. In contrast macrophages infiltrating glomeruli immediately after a second injection of Thy-1 antibody generated NO spontaneously and were unresponsive to alternative activation. beta-Glucuronidase expression was used as a second independent assay for macrophage activation and the results confirmed the observations made for NO. Furthermore, macrophages infiltrating the glomerulus after the second antibody injection exhibited a striking dichotomy in that 70% of the cells behave as programmed by interferon-gamma and 30% by transforming growth factor-beta. The results show that macrophage commitment occurs very early after monocyte migration and that infiltration itself does not invariably induce macrophage programming. It demonstrates that macrophages infiltrating inflamed glomeruli at the same time do not respond uniformly, but are capable of engaging different activation programs. This emphasizes the critical importance of the underlying disease process for macrophage functional development in an inflamed environment.