Recent evidence indicates that sperm output in human males has decreased by as much as 50% over the past several decades. No cause for the decline has been determined and little is understood about how toxicants affect sperm production. Thus, it would be useful to have a better understanding of mechanisms by which toxicants affect spermatogenesis in mammals. A variety of toxicants each appear to result in the failure of mature spermatids to be released by the Sertoli cells (SC). This similarity suggests that a common mechanism may underlie the action of many male reproductive toxins. The long-term objective of this project is to understand the cellular mechanism of reproductive toxicants, particularly toxicants that also induce the stress response. Cadmium or ethanol, both inducers of the stress or heat-shock response, result in failure of spermatid release in vivo. Inducers of the stress response also cause disruption of microfilaments and loss of tight junctions in cells in vivo and in vitro. Cadmium, heat-shock, and many other toxicants induce the synthesis of the low molecular weight heat-shock protein, hsp27. Hsp27 co- purifies with vinculin, a protein involved in linking microfilaments to cell plasma membranes. Hsp27 also inhibits actin polymerization in vitro. We hypothesize hsp27 is involved in regulation of microfilaments, possibly their attachment to membranes. We further hypothesize that many toxicants affect hsp27 synthesis in vivo and thereby affect abnormally the function of microfilaments and microfilament-dependent structures which may include tight junctions and tubulobulbar complexes in SC and other cell types. As a result, the blood-testis barrier is compromised and spermatid maturation is adversely affected causing failure of spermatid release by SC. To investigate this hypothesis, hsp27, actin microfilament structure, tight junctions and tubulobulbar complexes in SC will be studied. Light and electron microscopy, and immunological methods will be used to study hsp27 distribution and the structure of microfilaments, tight junctions, and tubulobulbar complexes in SC in normal rats and in animals exposed to the stress-inducer cadmium. Immunoprecipitation, affinity chromatography, and gel overlays and blots will be used to investigate interactions of hsp27 with junctional and microfilament-associated proteins. The effect of hsp2 phosphorylation on the ability of hsp27 to affect actin polymerization will be examined. It is expected that these studies will provide significant new knowledge about how toxicants affect cell function at a cell and molecular level, about microfilament function during spermatogenesis, and about the function of hsp27.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
1R01ES006265-01A1
Application #
3254541
Study Section
Toxicology Subcommittee 2 (TOX)
Project Start
1993-08-01
Project End
1996-07-01
Budget Start
1993-08-01
Budget End
1994-07-31
Support Year
1
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Jia, Y; Ransom, R F; Shibanuma, M et al. (2001) Identification and characterization of hic-5/ARA55 as an hsp27 binding protein. J Biol Chem 276:39911-8
Benndorf, R; Sun, X; Gilmont, R R et al. (2001) HSP22, a new member of the small heat shock protein superfamily, interacts with mimic of phosphorylated HSP27 ((3D)HSP27). J Biol Chem 276:26753-61
Liu, C; Gilmont, R R; Benndorf, R et al. (2000) Identification and characterization of a novel protein from Sertoli cells, PASS1, that associates with mammalian small stress protein hsp27. J Biol Chem 275:18724-31
Smoyer, W E; Ransom, R; Harris, R C et al. (2000) Ischemic acute renal failure induces differential expression of small heat shock proteins. J Am Soc Nephrol 11:211-21
Schafer, C; Clapp, P; Welsh, M J et al. (1999) HSP27 expression regulates CCK-induced changes of the actin cytoskeleton in CHO-CCK-A cells. Am J Physiol 277:C1032-43
Smoyer, W E; Mundel, P; Gupta, A et al. (1997) Podocyte alpha-actinin induction precedes foot process effacement in experimental nephrotic syndrome. Am J Physiol 273:F150-7
Mirkes, P E; Little, S A; Cornel, L et al. (1996) Induction of heat shock protein 27 in rat embryos exposed to hyperthermia. Mol Reprod Dev 45:276-84
Wu, W; Welsh, M J (1996) Rapid Coomassie blue staining and destaining of polyacrylamide gels. Biotechniques 20:386-8
Wu, W; Welsh, M J (1996) Expression of the 25-kDa heat-shock protein (HSP27) correlates with resistance to the toxicity of cadmium chloride, mercuric chloride, cis-platinum(II)-diammine dichloride, or sodium arsenite in mouse embryonic stem cells transfected with sense or antisen Toxicol Appl Pharmacol 141:330-9
Smoyer, W E; Gupta, A; Mundel, P et al. (1996) Altered expression of glomerular heat shock protein 27 in experimental nephrotic syndrome. J Clin Invest 97:2697-704

Showing the most recent 10 out of 16 publications