Modeling the structure of hsp 110, structural and functional homologies in the heat shock proteins & Glucose Regulated Proteins:
Heat shock proteins (hsps) and Glucose regulated proteins (grps) belong a class of proteins called molecular chaperones. These proteins are capable of binding to extended regions of denatured or newly synthesized proteins. This property makes it possible for these proteins to prevent the aggregation and mis-folding of the proteins to which they bind. Some molecular chaperones may actually assist the popper folding of the proteins to which they bind. Recently we have sequenced and begun to analyze a high molecular weight molecular chaperones called hsp 110 and Grp 170. Hsp 110 is 110 kDa molecular chaperone which belongs to a family of related proteins called hsp 70/DnaK. This work was done at Roswell Park Cancer Institute in Dr. John Subjek's group . Our model for hsp110 is based on the general similarities between hsp110 and its smaller relative hsp 70. This model has allowed us, to predict functional regions within the hsp110 molecule and construct mutations targeted to these functional regions in hsp 110. Analysis of the chaperoning activities of these mutations has born out our predictions. The domains B and H (marked on the figure) are are required (sufficient) for binding to denatured protein, while BL&H can bind denatured proteins and hold them in a conformation which will them to refold to the native state. Refolding can not take place in a simplified system. A crude cell extract is required for the refolding to occur. Efforts are being made to identify the components required for the folding activity. A similar analysis is being made of grp170 which is resident in the endoplasmic reticulum but shares many structural similarities with hsp 110.
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The Role of the Hsp110 gene in the development of Drosophila & C. elegans
Recently we have discovered that two different mutant alleles of the hsp110 gene in Drosophila, one of which is a P-element disruption and the other an x-ray generated mutation are lethal in the homozygous state. Both of these alleles effect the development of the tracheal system in larva. Both are lethal in the homozygous state, causing arrest of larval development. Similarly work with Dr. Wadsworth's lab has shown that knocking down the expression of the hsp110 gene is n C. elegans (a nematode worm commonly used as a model organism for molecular genetic research) by the RNAi technique has serious morphological consequences for the worm.. In both of these organisms it appears that hsp110 is required for the formation of cell-cell junctions required for organ formation during development. These observations suggest an important role in the assembly of cell junctions, a novel role for a heat shock protein.
Thermal Biology of ectothermic vertebrates:
The heat shock proteins are molecular chaperones (see above) who's synthesis can be increased greatly (induced) by thermal stress. The heat shock proteins can then deal with the increased load of denatured and mis-folded protein which accumulates in the cell as a result of the thermal stress or heat shock. In my laboratory we have investigated the induction of heat shock proteins in the the tissues of Eurycea bislineata (eastern two-lined salamander, below) exposed to heat shocks in the laboratory and to natural high temperatures in the field. We were able to show that 1. the severity of the heat shock predicts the extent of hsp 70 induction. 2. the response differed from tissue to tissue. 3. the response differed by time-temperature combination used in the shock. On a hot day probably 5-10% of a population of salamanders along a small stream are induced to synthesize hsps. Therefore, although the temperatures inducing hsp 70 in salamanders are at the high end of the scale of survivable temperatures for these animals, heat shock protein induction is probably necessary to the long term survival of salamander populations. A specimen of E. bislinata is shown below:
See Vitae for list of publications