Involvement of Cell Surface HSP90 in Cell Migration Reveals a Novel Role in the Developing Nervous System

Abstract

Heat shock protein HSP90 plays important roles in cellular regulation, primarily as a chaperone for a number of key intracellular proteins. We report here that the two HSP90 isoforms, ␣ and ␤, also localize on the surface of cells in the nervous system and are involved in their migration. A 94-kDa surface antigen, the 4C5 antigen, which was previously shown to be involved in migration processes during development of the nervous system, is shown to be identical to HSP90␣ using mass spectrometry analysis. This identity is further confirmed by immunoprecipitation experiments and by induction of 4C5 antigen expression in heat shock-treated embryonic rat brain cultures. Moreover, immunocytochemistry on live cerebellar rat cells reveals cell surface localization of both HSP90␣ and -␤. Cell migration from cerebellar and sciatic nerve explants is inhibited by anti-HSP90␣ and anti-HSP90␤ antibodies, similarly to the inhibition observed with monoclonal antibody 4C5. Moreover, immunostaining with rhodamine-phalloidin of migrating Schwann cells cultured in the presence of antibodies against both ␣ and ␤ isoforms of HSP90 reveals that HSP90 activity is associated with actin cytoskeletal organization, necessary for lamellipodia formation.The development of the vertebrate nervous system depends on extensive cell migration, which allows different cell types to reach their final destination and establish the composite organization of the adult nervous system. Cell migration is a complex process, which requires the coordination of many molecular and cellular events such as cell-cell recognition, adhesion, transmembrane signaling, and cell motility (1-23). The mechanisms underlying these processes involve orchestrated interactions between a large number of molecules (10, 24). Emerging evidence suggests that many proteins in the nervous system have multiple distinct functions. Thus, molecules involved in migration processes have been shown to participate additionally in other developmental events. These include the cell adhesion molecules (CAMs), which regulate axonal growth and regeneration (25); integrins, which mediate cell proliferation and synaptic plasticity (26); and neuregulins that promote neuronal differentiation and regulate glial commitment, proliferation, survival, and differentiation (27). We report here that heat shock protein 90 (HSP90) 1 is also a multifunctional protein, processing a novel role in neuronal migration. HSP90 is a highly conserved molecule with a wide distribution in various species. It acts as capacitor of morphological evolution in Drosophila melanogaster (28 -30). It also functions as a chaperone in unstressed cells, specifically involved in the folding or conformational regulation of central signal transduction molecules, including steroid hormone receptors and proto-oncogene kinases (31, 32). Moreover, it is a protective agent under stress conditions and is involved in protein renaturation and refolding (33). In the developing mammalian nervous system, HSP90 is highly expressed in the G 0 phase ...

The neuroblastoma tumour-suppressor TrkAI and its oncogenic alternative TrkAIII splice variant exhibit geldanamycin-sensitive interactions with Hsp90 in human neuroblastoma cells

“…However, because of lack of adequate mono-specific anti-Hsp90a and Hsp90b antibodies for FACS and IF, we are unable to state whether Hsp90a, in addition to Hsp90b, is also expressed at the SH-SY5Y cell surface. Cell surface Hsp90 (a/b) expression was also detected in pcDNA and TrkAIII transfectants, adding SH-SY5Y cells to other tumour and normal cell types that express cell surface Hsp90 (a/b) (Becker et al, 2004;Sidera et al, 2004Sidera et al, , 2008 and TrkAI to other cell surface receptors that depend on interaction with Hsp90 for stability (Vega and De Maio, 2003;Peng et al, 2005).…”

A small molecule cell-impermeant Hsp90 antagonist inhibits tumor cell motility and invasion

“…Cell surface expression of Hsp90 has been observed on melanoma cells, fibrosarcoma cells and neuronal cells (Erkeller-Yuksel et al, 1992;Becker et al, 2004;Eustace et al, 2004;Sidera et al, 2004). In melanoma cells, cell surface Hsp90 expression correlates positively with metastatic potential (Becker et al, 2004), and inhibition of cell surface Hsp90 with antibody (Sidera et al, 2004) or GA coupled to cell-impermeable agarose beads (Eustace et al, 2004) has been reported to reduce cell migration in vitro. Thus, cell surface Hsp90 may play a role in cancer cell motility and metastasis distinct from but perhaps overlapping with its intracellular chaperone function.…”

Mesencephalic Astrocyte-derived Neurotrophic Factor (MANF) Secretion and Cell Surface Binding Are Modulated by KDEL Receptors

“…For example, GRP78 was first identified at the surface of malignant lymphocytes (17), and the elevated levels observed on the surface of malignant cells have been exploited to successfully target and kill these cells with small molecules (18,19). GRP94 is similarly detected at the membrane in the nervous system, where it was found to regulate cell migration (20).…”