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Effect of GroEL-like heat shock protein on epithelial behavior

University of British Columbia

This research work focused on the effect of heat shock protein 60 (hsp60) from a periodontopathogen Actinobacillus actinomycetemcomitans on keratinocyte behavior and regulation of cell signaling. The research project encompasses four aspects. In the first study, we investigated whether bacterial hsp60 can alter epithelial cell mitogen-activated protein kinase (MAPK) signaling and cell proliferation. The results showed that hsp60 greatly increased viable cell number in culture. Hsp60-induced phosphorylation of ERK, JNK, and p38 was dose- and time-dependent. The association between hsp60-induced cell proliferation and activation of ERK and p38 was determined by PD 98059 (a specific inhibitor of MEK) and SB 203580 (a specific inhibitor of p38). The results indicated that hsp60 was able to induce phosphorylation of ERK1/2 and thereby promote keratinocyte proliferation. In the second study, the effect of bacterial hsp60 on stress-induced cell death was investigated. The results showed that hsp60 significantly protected against UV radiation- and heat shockinduced cell death. Hsp60 pretreatment strongly induced activation of ERK1/2 and inhibited UV radiation-induced activation of caspase 3, an excecutioner enzyme of apoptosis. ERK pathway specific inhibitor partially blocks this hsp60 inhibitory effect. The results indicated that UV radiation induces apoptosis through the p38/caspase3 pathway and hsp60 protects keratinocytes from apoptosis by activation of ERK, which in turn inhibits stress-induced caspase 3 activation. In the third study, long-term effects of hsp60 on keratinocytes were studied by measuring total and viable cell number, production of TNFoc, synthesis of cellular hsp60 and hsp70, and MAPK phosphorylation. The results showed that in a prolonged culture, hsp60 increased cell death, reduced the ratio of phosphorylated ERK:p38, increased TNFa production, and inhibited heat shock-induced cellular hsp60 synthesis. In the fourth study, the effect of hsp60s on keratinocyte migration was investigated. The results showed that hsp60 from bacteria and human promoted cell migration by 2-5-fold. Hsp60 specifically reduced a6 integrin subunit expression and cell surface levels that may facilitate tail detachment and migration of keratinocytes. The pretreatment of the cells with SB 203580 and PD 98059 showed that activity of both p38 and ERK-pathways were involved in the stimulation of cell migration by exogenous hsp60.

Thesis/Dissertation

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2009-10-05

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http://hdl.handle.net/2429/13570

Dental Science

University of British Columbia

UBCV

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