Endoplasmic Reticulum-resident Heat Shock Protein 90 (HSP90) Isoform Glucose-regulated Protein 94 (GRP94) Regulates Cell Polarity and Cancer Cell Migration by Affecting Intracellular Transport

Abstract

Heat shock protein 90 (HSP90) is a molecular chaperone that is up-regulated in cancer and is required for the folding of numerous signaling proteins. Consequently, HSP90 represents an ideal target for the development of new anti-cancer agents. The human HSP90 isoform, glucose-regulated protein 94 (GRP94), resides in the endoplasmic reticulum and regulates secretory pathways, integrins, and Toll-like receptors, which contribute to regulating immunity and metastasis. However, the cellular function of GRP94 remains underinvestigated. We report that GRP94 knockdown cells are defective in intracellular transport and, consequently, negatively impact the trafficking of F-actin toward the cellular cortex, integrin ␣2 and integrin ␣L toward the cell membrane and filopodia, and secretory vesicles containing the HSP90␣-AHA1-survivin complex toward the leading edge. As a result, GRP94 knockdown cells form a multipolar spindle instead of bipolar morphology and consequently manifest a defect in cell migration and adhesion.Cell migration is the process by which cells move during developmental morphogenesis, tissue repair and regeneration, and cancer metastasis. During metastasis, cancer cells polarize in response to chemokines or environmental cues originating from the extracellular matrix (ECM). 2 With the assistance of microtubules, the microtubule-organizing center and the Golgi apparatus orient toward the direction of migration to aid vesicular transport toward the leading edge (1, 2). At the leading edge of the polarized cell, actin polymerization occurs rapidly to form lamellipodia, from which slender cytoplasmic projections called filopodia develop (3-5). These filopodia play roles in sensing, migration, cell-cell interactions, and adhesion (6). Adhesion of filopodia and lamellipodia to the ECM occurs through integrin receptors. Integrin receptors are a large superfamily of heterodimeric receptors that bind ECM ligands or cognate ligands on adjacent cells. The macromolecular assembly through which mechanical force and regulatory signals are transmitted between the ECM and a neighboring cell is described as a focal adhesion, which is composed of integrins, adapter proteins, and signaling molecules (7). The focal adhesion complex undergoes endo-exocytic cycles, and disruption of the endosomal transport or exocytic fusion of recycling vesicles affects cell polarity and migration (8, 9).The endoplasmic reticulum (ER) is the manufacturing site of newly synthesized proteins that are folded and targeted to their destination. The ER works continuously with the outer layer of the nuclear envelope but separate from the Golgi apparatus. Protein transport from the ER to Golgi occurs through coatomer I-and II-coated vesicles, with final transport to the plasma membrane occurring via endosomes. Cell migration requires the transport of proteins to the leading edge to establish cell polarity, filopodia and lamellipodia formation, adhesion, signaling, and translocation. In addition, several secretory proteins are required at the leading...

Endoplasmic reticulum chaperone Gp96 controls actomyosin dynamics and protects against pore‐forming toxins

“…Notably, we demonstrate that these events also occur during cell migration and assembly of uropod-like WRAMP structures, suggesting a common mechanism to regulate PM retraction and cytoskeletal dynamics during PFT-induced PM blebbing and cell migration [21,22,29]. Consistent with our findings, NMII has established roles in both processes [28,33] and Gp96 was recently shown to promote cell polarity and migration [34,35]. How the NMHCIIA-Gp96 interplay coordinates cytoskeleton dynamics and PM remodelling remains elusive.…”

“…Different studies have suggested that polarized secretion of lysosomes and redistribution of ER and/or endosomal compartments regulate uropod dynamics and trailing edge retraction during migration of cancer cells or leucocytes [22,36]. We show that ER and LAMP1-positive compartments localized within NMHCIIA bundles and Gp96 was proposed to modulate polarity via vesicular trafficking [35]. Additionally, NMHCIIA can control polarized secretion [37] and organelle positioning [38] and was recently shown to mediate lysosomal exocytosis in PFT-wounded cells [39].…”

Proteomics analysis of human breast milk to assess breast cancer risk

“…The main function of this protein is in the folding of other proteins. However, other members of heat shock protein family have been shown to be upregulated in cancer and play a role in immune system and metastasis . The levels of glucose‐regulated protein 94, which is an isoform of heat shock protein 90 were compared in two replicates of cancer tissues of prostate, BC metastatic to liver, and lung cancer versus normal tissues from the same person using Western blot analysis and no heat shock protein 90 was observed in controls, but there were positive results for cancer samples .…”

Development of Glucose Regulated Protein 94-Selective Inhibitors Based on the BnIm and Radamide Scaffold

“…42 Similarly, selective inhibition of Grp94 resulted in the degradation of integrin α 2 (Figure 7A,B). Integrin α 2 forms a heterodimer with integrin β 1 on the cell surface, 38 which is responsible for binding to collagen in the extracellular matrix to promote metastasis and invasion.…”