Differential effect of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) on alpha B-crystallin and hsp70 gene expression in murine cell lines

Expression of alphaB-crystallin in glia cells during lesional development in multiple sclerosis

The small heat shock protein alphaB-crystallin was recently identified as a dominant human T-cell antigen in myelin derived from multiple sclerosis (MS) patients. Using immunohistochemical techniques, oligodendrocytes as well as astrocytes in MS lesions were shown to express alphaB-crystallin. In the present study we examined the expression of alphaB-crystallin, human natural killer cell marker (HNK-1; as a marker for immature oligodendrocytes) and heat shock protein 60 (hsp60) in glia cells at different stages of MS lesion development i.e. in early active lesions, late active lesions and inactive lesions. The results demonstrate that already at the earliest stages of lesional development a subpopulation of oligodendrocytes express detectable levels of alphaB-crystallin. In active lesions about 5-10% of all oligodendrocytes were found to express alphaB-crystallin, whereas in inactive lesions the relative number of alphaB-crystallin-expressing oligodendrocytes was approximately tenfold less. For astrocytes the relative number of alphaB-crystallin-expressing cells was 40-50% for all three types of lesions. Also, alphaB-crystallin-expressing oligodendrocytes and astrocytes displayed different patterns of distribution in lesional areas. These data suggest different regulatory pathways for alphaB-crystallin expression in either type of glia cell. No correlation was found between expression patterns of HNK-1 and alphaB-crystallin indicating that the subpopulation of alphaB-crystallin-expressing oligodendrocytes consisted of both mature and immature oligodendrocytes. In addition, no correlation was found between expression of hsp60 and alphaB-crystallin in MS lesions suggesting different regulatory pathways for either hsp.

Transcription regulation of alpha B-crystallin in astrocytes: analysis of HSF and AP1 activation by different types of physiological stress

The coordinated cellular responses to physiological stress are known to be effected in part by the activation of heat-shock factor 1, a transcriptional activator protein capable of binding to, and inducing transcription from genes containing heat shock elements. Other stress responsive signal transduction pathways also exist including the stress activated protein kinase cascade that regulates the activity of the transcription factor AP1. We have examined the expression of the low molecular stress proteins, heat shock protein 27 and alpha B-crystallin in astrocytes in response to physiological stress of different types and asked what component of this induction is effected at the transcriptional level and whether activation of heat shock factor 1 and AP1 might account for these events. We have found that stress regulated induction of alpha B-crystallin has a strong transcriptional component and that it may be effected by at least two different transcriptional mechanisms. In one set of phenomena, represented here by cadmium exposure, alpha B-crystallin and heat shock protein 27 are coordinately regulated and this occurs in the presence of activated heat shock factor 1. In the second series of phenomena, represented here by hypertonic stress, alpha B-crystallin is induced in the absence of heat shock factor activation and in the absence of any corresponding change in heat shock protein 27 expression. Although hypertonic stress does activate an AP1-like binding activity, the AP1 consensus binding site in the alpha B-crystallin promoter does not appear to be a target for this hypertonic stress inducible activity. These data suggest that the hypertonic stress response is effected through a heat shock factor independent mechanism and that hypertonic stress regulated induction of alpha B-crystallin does not directly depend on the SAPK pathway and AP1 activity.