Alpha B crystallin expression in response to hormone, oncogenes and stress.
alpha B crystallin is one of the major eye lens proteins and it is abundantly expressed in many non-lenticular tissues as well. The alpha B crystallin protein sequence is similar to that of small heat shock proteins and we could demonstrate that alpha B crystallin does indeed accumulate in response to heat shock and other forms of stress. Moreover, ectopic expression of alpha B crystallin establishes a state of thermotolerance. Glucocorticoid hormones activate the alpha B crystallin gene with a delayed kinetics. Induced expression of the Ha-ras oncogene accelerates hormone-mediated gene induction. A shorter promoter sequence is required for the ras supported hormone response. However, sustained Ha-ras oncogene expression attenuates glucocorticoid-triggered induction of the alpha B crystallin gene completely. Whereas the small heat shock protein Hsp27 is overexpressed in many human mammary carcinomas, we observed the frequent absence of alpha B crystallin in these tumors but not in the normal breast tissue. In contrast, overexpression of alpha B crystallin has been frequently observed in non-neuronal brain tumors.
Klemenz
R
R
Department of Pathology, University Hospital, Zürich, Switzerland.
Scheier
B
B
Müller
A
A
Steiger
R
R
Aoyama
A
A
D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D003459:Crystallins / Q000096:biosynthesis*; D015870:Gene Expression; D011905:Genes, ras; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006728:Hormones / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D009928:Organ Specificity; D013312:Stress, Physiological
D003459:Crystallins; D006360:Heat-Shock Proteins; D006728:Hormones