Enhanced delivery of antibodies across the blood-brain barrier via TEMs with inherent receptor-mediated phagocytosis

BACKGROUND

The near impermeability of the blood-brain barrier (BBB) and the unique neuroimmune environment of the CNS prevents the effective use of antibodies in neurological diseases. Delivery of biotherapeutics to the brain can be enabled through receptor-mediated transcytosis via proteins such as the transferrin receptor, although limitations such as the ability to use Fc-mediated effector function to clear pathogenic targets can introduce safety liabilities. Hence, novel delivery approaches with alternative clearance mechanisms are warranted.

METHODS

Binders that optimized transport across the BBB, known as transcytosis-enabling modules (TEMs), were identified using a combination of antibody discovery techniques and pharmacokinetic analyses. Functional activity of TEMs were subsequently evaluated by imaging for the ability of myeloid cells to phagocytose target proteins and cells.

FINDINGS

We demonstrated significantly enhanced brain exposure of therapeutic antibodies using optimal transferrin receptor or CD98 TEMs. We found that these modules also mediated efficient clearance of tau aggregates and HER2+ tumor cells via a non-classical phagocytosis mechanism through direct engagement of myeloid cells. This mode of clearance potentially avoids the known drawbacks of FcγR-mediated antibody mechanisms in the brain such as the neurotoxic release of proinflammatory cytokines and immune cell exhaustion.

CONCLUSIONS

Our study reports a new brain delivery platform that harnesses receptor-mediated transcytosis to maximize brain uptake and uses a non-classical phagocytosis mechanism to efficiently clear pathologic proteins and cells. We believe these findings will transform therapeutic approaches to treat CNS diseases.

FUNDING

This research was funded by Janssen, Pharmaceutical Companies of Johnson & Johnson.

Efficient Golgi Forward Trafficking Requires GOLPH3-Driven, PI4P-Dependent Membrane Curvature

Vesicle budding for Golgi-to-plasma membrane trafficking is a key step in secretion. Proteins that induce curvature of the Golgi membrane are predicted to be required, by analogy to vesicle budding from other membranes. Here, we demonstrate that GOLPH3, upon binding to the phosphoinositide PI4P, induces curvature of synthetic membranes in vitro and the Golgi in cells. Moreover, efficient Golgi-to-plasma membrane trafficking critically depends on the ability of GOLPH3 to curve the Golgi membrane. Interestingly, uncoupling of GOLPH3 from its binding partner MYO18A results in extensive curvature of Golgi membranes, producing dramatic tubulation of the Golgi, but does not support forward trafficking. Thus, forward trafficking from the Golgi to the plasma membrane requires the ability of GOLPH3 both to induce Golgi membrane curvature and to recruit MYO18A. These data provide fundamental insight into the mechanism of Golgi trafficking and into the function of the unique Golgi secretory oncoproteins GOLPH3 and MYO18A.

The role of Tks adaptor proteins in invadopodia formation, growth and metastasis of melanoma

Metastatic cancer cells are characterized by their ability to degrade and invade through extracellular matrix. We previously showed that the Tks adaptor proteins, Tks4 and Tks5, are required for invadopodia formation and/or function in Src-transformed fibroblasts and a number of human cancer cell types. In this study, we investigated the role of Tks adaptor proteins in melanoma cell invasion and metastasis. Knockdown of either Tks4 or Tks5 in both mouse and human melanoma cell lines resulted in a decreased ability to form invadopodia and degrade extracellular matrix. In addition, Tks-knockdown melanoma cells had decreased proliferation in a 3-dimensional type l collagen matrix, but not in 2-dimensional culture conditions. We also investigated the role of Tks proteins in melanoma progression in vivo using xenografts and experimental metastasis assays. Consistent with our in vitro results, reduction of Tks proteins markedly reduced subcutaneous melanoma growth as well as metastatic growth in the lung. We explored the clinical relevance of Tks protein expression in human melanoma specimens using a tissue microarray. Compared to non-malignant nevi, both Tks proteins were highly expressed in melanoma tissues. Moreover, metastatic melanoma cases showed higher expression of Tks5 than primary melanoma cases. Taken together, these findings suggest the importance of Tks adaptor proteins in melanoma growth and metastasis in vivo, likely via functional invadopodia formation.

A Daple-Akt feed-forward loop enhances noncanonical Wnt signals by compartmentalizing β-catenin

Balance between canonical and noncanonical Wnt pathways controls the β-catenin transcriptional program; how the noncanonical pathway antagonizes the canonical pathway remains unclear. We show that Daple, an enhancer of noncanonical Wnt signals, accomplishes that goal by dictating the subcellular distribution of β-catenin in cells.

Cellular proliferation is antagonistically regulated by canonical and noncanonical Wnt signals; their dysbalance triggers cancers. We previously showed that a multimodular signal transducer, Daple, enhances PI3-K→Akt signals within the noncanonical Wnt signaling pathway and antagonistically inhibits canonical Wnt responses. Here we demonstrate that the PI3-K→Akt pathway serves as a positive feedback loop that further enhances noncanonical Wnt signals by compartmentalizing β-catenin. By phosphorylating the phosphoinositide- (PI) binding domain of Daple, Akt abolishes Daple’s ability to bind PI3-P-enriched endosomes that engage dynein motor complex for long-distance trafficking of β-catenin/E-cadherin complexes to pericentriolar recycling endosomes (PCREs). Phosphorylation compartmentalizes Daple/β-catenin/E-cadherin complexes to cell–cell contact sites, enhances noncanonical Wnt signals, and thereby suppresses colony growth. Dephosphorylation compartmentalizes β-catenin on PCREs, a specialized compartment for prolonged unopposed canonical Wnt signaling, and enhances colony growth. Cancer-associated Daple mutants that are insensitive to Akt mimic a constitutively dephosphorylated state. This work not only identifies Daple as a platform for cross-talk between Akt and the noncanonical Wnt pathway but also reveals the impact of such cross-talk on tumor cell phenotypes that are critical for cancer initiation and progression.

The GOLPH3 pathway regulates Golgi shape and function and is activated by DNA damage

The Golgi protein GOLPH3 binds to PtdIns(4)P and MYO18A, linking the Golgi to the actin cytoskeleton. The GOLPH3 pathway is essential for vesicular trafficking from the Golgi to the plasma membrane. A side effect of GOLPH3-dependent trafficking is to generate the extended ribbon shape of the Golgi. Perturbation of the pathway results in changes to both Golgi morphology and secretion, with functional consequences for the cell. The cellular response to DNA damage provides an example of GOLPH3-mediated regulation of the Golgi. Upon DNA damage, DNA-PK phosphorylation of GOLPH3 increases binding to MYO18A, activating the GOLPH3 pathway, which consequently results in Golgi fragmentation, reduced trafficking, and enhanced cell survival. The PtdIns(4)P/GOLPH3/MYO18A/F-actin pathway provides new insight into the relationship between Golgi morphology and function, and their regulation.

GOLPH3 links the Golgi, DNA damage, and cancer

GOLPH3 is the first example of an oncogene that functions in secretory trafficking at the Golgi. The discovery of GOLPH3's roles in both cancer and Golgi trafficking raises questions about how GOLPH3 and the Golgi contribute to cancer. Our recent investigation of the regulation of GOLPH3 revealed a surprising response by the Golgi upon DNA damage that is mediated by DNA-PK and GOLPH3. These results provide new insight into the DNA damage response with important implications for understanding the cellular response to standard cancer therapeutic agents.

Abstract 3155: Tks adaptor proteins and invadopodia formation in the growth and metastasis of melanoma

Invadopodia are actin-based proteolytic structures which facilitate cancer cell invasion and metastasis. While it was previously believed that invadopodia are not required for tumor cell growth, based on studies in monolayer cell culture, more recently we have noted a role for invadopodia proteins in growth in more physiological 3-dimensional (3D) extracellular matrix contexts. From previous work in our lab, the Tks adaptor proteins with 5 (Tks5) and 4 (Tks4) SH3 domains, respectively, were identified as Src kinase substrates and both are essential molecules for functional invadopodia formation in mouse and human cancer cells.

Here, we assess the roles of the Tks adaptors in melanoma tumor growth and invasion both in vivo and in vitro. To address the mechanism as to how the Tks adaptors control tumor growth and invasion, in vitro 3D growth assays in collagen I were performed. Knockdown of either Tks4 or Tks5 in C8161.9 or A375 melanoma cells decreased 3D growth in collagen I, a process that also appeared to be dependent upon metalloproteinase (MMP) activity. Interestingly, knockdown of either Tks4 or Tks5 in A375 melanoma cells decreased cell-surface expression of MT1-MMP, a key protease involved in tumor growth and metastasis. In vivo tumor growth and metastasis assays in mice using human and mouse melanoma cells depleted of Tks4 or Tks5 by shRNA revealed roles for the Tks adaptors in both the size and the number of lung metastases. Finally, analysis of a human melanoma tissue array with a Tks5 antibody, and RNAseq data, indicates that Tks5 expression is increased in lymph node and other metastases in comparison to nevi and primary sites.

These data suggest that the Tks adaptors control melanoma tumor growth and invasion by regulating invadopodia formation and perhaps also cell surface expression of MT1-MMP, and thus contribute to melanoma progression.

Citation Format: Shinji Iizuka, Christine M. Gould, Matthew D. Buschman, Diaz Begoña, Christopher Abdullah, Sara Courtneidge. Tks adaptor proteins and invadopodia formation in the growth and metastasis of melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3155. doi:10.1158/1538-7445.AM2014-3155

DNA damage triggers Golgi dispersal via DNA-PK and GOLPH3

The response to DNA damage, which regulates nuclear processes such as DNA repair, transcription, and cell cycle, has been studied thoroughly. However, the cytoplasmic response to DNA damage is poorly understood. Here, we demonstrate that DNA damage triggers dramatic reorganization of the Golgi, resulting in its dispersal throughout the cytoplasm. We further show that DNA-damage-induced Golgi dispersal requires GOLPH3/MYO18A/F-actin and the DNA damage protein kinase, DNA-PK. In response to DNA damage, DNA-PK phosphorylates GOLPH3, resulting in increased interaction with MYO18A, which applies a tensile force to the Golgi. Interference with the Golgi DNA damage response by depletion of DNA-PK, GOLPH3, or MYO18A reduces survival after DNA damage, whereas overexpression of GOLPH3, as is observed frequently in human cancers, confers resistance to killing by DNA-damaging agents. Identification of the DNA-damage-induced Golgi response reveals an unexpected pathway through DNA-PK, GOLPH3, and MYO18A that regulates cell survival following DNA damage.

GOLPH3L antagonizes GOLPH3 to determine Golgi morphology

GOLPH3 is a ubiquitous PI4P effector, critical for Golgi function, and also an oncogene. GOLPH3L, a paralogue in vertebrates, also binds PI4P and localizes to the Golgi, but its expression is restricted to secretory cells. Despite some similarities to GOLPH3, GOLPH3L fails to interact with myosin 18A and functions at the Golgi to antagonize GOLPH3.

GOLPH3 is a phosphatidylinositol-4-phosphate (PI4P) effector that plays an important role in maintaining Golgi architecture and anterograde trafficking. GOLPH3 does so through its ability to link trans-Golgi membranes to F-actin via its interaction with myosin 18A (MYO18A). GOLPH3 also is known to be an oncogene commonly amplified in human cancers. GOLPH3L is a GOLPH3 paralogue found in all vertebrate genomes, although previously it was largely uncharacterized. Here we demonstrate that although GOLPH3 is ubiquitously expressed in mammalian cells, GOLPH3L is present in only a subset of tissues and cell types, particularly secretory tissues. We show that, like GOLPH3, GOLPH3L binds to PI4P, localizes to the Golgi as a consequence of its PI4P binding, and is required for efficient anterograde trafficking. Surprisingly, however, we find that perturbations of GOLPH3L expression produce effects on Golgi morphology that are opposite to those of GOLPH3 and MYO18A. GOLPH3L differs critically from GOLPH3 in that it is largely unable to bind to MYO18A. Our data demonstrate that despite their similarities, unexpectedly, GOLPH3L antagonizes GOLPH3/MYO18A at the Golgi.

Interleukin-15 enhances proteasomal degradation of bid in normal lymphocytes: implications for large granular lymphocyte leukemias

Large granular lymphocyte (LGL) leukemia is a clonal proliferative disease of T and natural killer (NK) cells. Interleukin (IL)-15 is important for the development and progression of LGL leukemia and is a survival factor for normal NK and T memory cells. IL-15 alters expression of Bcl-2 family members, Bcl-2, Bcl-XL, Bim, Noxa, and Mcl-1; however, effects on Bid have not been shown. Using an adoptive transfer model, we show that NK cells from Bid-deficient mice survive longer than cells from wild-type control mice when transferred into IL-15-null mice. In normal human NK cells, IL-15 significantly reduces Bid accumulation. Decreases in Bid are not due to alterations in RNA accumulation but result from increased proteasomal degradation. IL-15 up-regulates the E3 ligase HDM2 and we find that HDM2 directly interacts with Bid. HDM2 suppression by short hairpin RNA increases Bid accumulation lending further support for HDM2 involvement in Bid degradation. In primary leukemic LGLs, Bid levels are low but are reversed with bortezomib treatment with subsequent increases in LGL apoptosis. Overall, these data provide a novel molecular mechanism for IL-15 control of Bid that potentially links this cytokine to leukemogenesis through targeted proteasome degradation of Bid and offers the possibility that proteasome inhibitors may aid in the treatment of LGL leukemia.

The novel adaptor protein Tks4 (SH3PXD2B) is required for functional podosome formation

Metastatic cancer cells have the ability to both degrade and migrate through the extracellular matrix (ECM). Invasiveness can be correlated with the presence of dynamic actin-rich membrane structures called podosomes or invadopodia. We showed previously that the adaptor protein tyrosine kinase substrate with five Src homology 3 domains (Tks5)/Fish is required for podosome/invadopodia formation, degradation of ECM, and cancer cell invasion in vivo and in vitro. Here, we describe Tks4, a novel protein that is closely related to Tks5. This protein contains an amino-terminal Phox homology domain, four SH3 domains, and several proline-rich motifs. In Src-transformed fibroblasts, Tks4 is tyrosine phosphorylated and predominantly localized to rosettes of podosomes. We used both short hairpin RNA knockdown and mouse embryo fibroblasts lacking Tks4 to investigate its role in podosome formation. We found that lack of Tks4 resulted in incomplete podosome formation and inhibited ECM degradation. Both phenotypes were rescued by reintroduction of Tks4, whereas only podosome formation, but not ECM degradation, was rescued by overexpression of Tks5. The tyrosine phosphorylation sites of Tks4 were required for efficient rescue. Furthermore, in the absence of Tks4, membrane type-1 matrix metalloproteinase (MT1-MMP) was not recruited to the incomplete podosomes. These findings suggest that Tks4 and Tks5 have overlapping, but not identical, functions, and implicate Tks4 in MT1-MMP recruitment and ECM degradation.

The Proinflammatory Cytokine Interleukin-18 Alters Multiple Signaling Pathways to Inhibit Natural Killer Cell Death

The proinflammatory cytokine, interleukin-18 (IL-18), is a natural killer (NK) cell activator that induces NK cell cytotoxicity and interferon-gamma (IFN-gamma) expression. In this report, we define a novel role for IL-18 as an NK cell protective agent. Specifically, IL-18 prevents NK cell death initiated by different and distinct stress mechanisms. IL-18 reduces NK cell self-destruction during NK-targeted cell killing, and in the presence of staurosporin, a potent apoptotic inducer, IL-18 reduces caspase-3 activity. The critical regulatory step in this process is downstream of the mitochondrion and involves reduced cleavage and activation of caspase-9 and caspase-3. The ability of IL-18 to regulate cell survival is not limited to a caspase death pathway in that IL-18 augments tumor necrosis factor (TNF) signaling, resulting in increased and prolonged mRNA expression of c-apoptosis inhibitor 2 (cIAP2), a prosurvival factor and caspase-3 inhibitor, and TNF receptor-associated factor 1 (TRAF1), a prosurvival protein. The cumulative effects of IL-18 define a novel role for this cytokine as a molecular survival switch that functions to both decrease cell death through inhibition of the mitochondrial apoptotic pathway and enhance TNF induction of prosurvival factors.