HSP70 production and inhibition of cell proliferation in Molt-4 T-cells after cell-to-cell transmission of HTLV-I: effect of PGA1

Heat shock cognate protein 70 gene is required for prevention of apoptosis induced by WSSV infection

Here, we show that heat shock cognate protein 70 (Hsc70) in shrimp cells can inhibit apoptosis induced by white spot syndrome virus (WSSV) infection. Caspase-3 protease activity of hemocytes increased significantly, correlating with a reduction in endogenous Hsc70 late in WSSV infection. Hsc70 dsRNA caused a significant increase in caspase-3 activity in the hemocytes of non-infected shrimp and WSSV-infected shrimp. We propose that upregulation of Hsc70 expression early in WSSV infection may also be used to prevent premature apoptotic cell death, and the precipitous downregulation of Hsc70 late in WSSV infection may lead to the timed induction of apoptosis.

Role of Heat Shock Proteins in Viral Infection

One of the most intriguing and less known aspects of the interaction between viruses and their host is the impact of the viral infection on the heat shock response (HSR). While both a positive and a negative role of different heat shock proteins (HSP) in the control of virus replication has been hypothesized, HSP function during the virus replication cycle is still not well understood. This chapter describes different aspects of the interactions between viruses and heat shock proteins during infection of mammalian cells: the first part focuses on the modulation of the heat shock response by human viral pathogens; the second describes the interactions of HSP and other chaperones with viral components, and their function during different steps of the virus replication cycle; the last part summarizes our knowledge on the effect of hyperthermia and HSR modulators on virus replication.

Controlled delivery of heat shock protein using an injectable microsphere/hydrogel combination system for the treatment of myocardial infarction

Myocardial infarction causes a high rate of morbidity and mortality worldwide, and heat shock proteins as molecular chaperones have been attractive targets for protecting cardiomyoblasts under environmental stimuli. In this study, in order to enhance the penetration of heat shock protein 27 (HSP27) across cell membranes, we fused HSP27 with transcriptional activator (TAT) derived from human immunodeficiency virus (HIV) as a protein transduction domain (PTD). We loaded the fusion protein (TAT-HSP27) into microsphere/hydrogel combination delivery systems to control the release behavior for prolonged time periods. We found that the release behavior of TAT-HSP27 was able to be controlled by varying the ratio of PLGA microspheres and alginate hydrogels. Indeed, the released fusion protein maintained its bioactivity and could recover the proliferation of cardiomyoblasts cultured under hypoxic conditions. This approach to controlling the release behavior of TAT-HSP27 using microsphere/hydrogel combination delivery systems may be useful for treating myocardial infarction in a minimally invasive manner.

Chaperones in cell cycle regulation and mitogenic signal transduction: a review

Chaperones/heat shock proteins (HSPs) of the HSP90 and HSP70 families show elevated levels in proliferating mammalian cells and a cell cycle-dependent expression. They transiently associate with key molecules of the cell cycle control system such as Cdk4, Wee-1, pRb, p53, p27/Kip1 and are involved in the nuclear localization of regulatory proteins. They also associate with viral oncoproteins such as SV40 super T, large T and small t antigen, polyoma large and middle S antigen and EpsteinBarr virus nuclear antigen. This association is based on a J-domain in the viral proteins and may assist their targeting to the pRb/E2F complex. Small HSPs and their state of phosphorylation and oligomerization also seem to be involved in proliferation and differentiation. Chaperones/HSPs thus play important roles within cell cycle processes. Their exact functioning, however, is still a matter of discussion. HSP90 in particular, but also HSP70 and other chaperones associate with proteins of the mitogen-activated signal cascade, particularly with the Src kinase, with tyrosine receptor kinases, with Raf and the MAP-kinase activating kinase (MEK). This apparently serves the folding and translocation of these proteins, but possibly also the formation of large immobilized complexes of signal transducing molecules (scaffolding function).

Interferon-alpha inhibits the emergence of cellular stress response-dependent morbillivirus large plaque variants

Cellular levels of heat shock proteins (HSPs) are elevated in response to physiologic states accompanying acute virus infection (e.g. fever). The objective of the present work was to define the antiviral effect of purified human lymphoblastoid IFN in the presence of HSP over-expression. For this purpose, canine distemper virus (CDV) was used since the response of CDV transcription and persistent infection phenotype to elevated HSP is characterized. First, the effect of elevated HSP on CDV lytic infection phenotype in Vero and CV1 cells was defined, and results extended to the closely related measles virus (MV). Cells expressing elevated levels of the major inducible 70-kDa HSP (hsp72) supported the emergence of large plaque variants of both CDV and MV from small plaque purified inocula. IFN treatment concurrent with infection caused a dosage-dependent reduction in the expression of large plaque variants without affecting hsp72 levels or total plaque number. In contrast to the stress response-induced large plaque variant, small plaques were resistant to the antiviral effects of IFN. These data demonstrate the ability of IFN to selectively abrogate the pro-viral effects of HSP over-expression, inhibiting the formation of a plaque phenotype that is correlated to enhanced virulence in animal models of morbillivirus encephalitis.

Viral infection

The relationship between viruses and the cellular stress response is a multifaceted and complex phenomenon which depends on the structural and genetic characteristics of the virus, on the type of infection, as well as on the environmental conditions. It is now well documented that infection of mammalian cells by several types of RNA and DNA viruses often results in alterations of the cellular stress response. Interactions between stress proteins and viral components have been described in a large variety of experimental models at different stages of the viral life cycle, depending on the type of virus and host cell. The presence of heat shock proteins in intact virions has also been described. On the other hand, induction of HSP expression by hyperthermia or other agents results in alterations of the virus replication cycle during acute or persistent infections of mammalian cells, and a possible role of heat shock proteins in the beneficial effect of fever and local hyperthermia during acute infection has been hypothesized. This chapter describes the different aspects of the interaction between viruses and the stress response, and discusses the possible role of stress proteins in the control of virus replication and morphogenesis.