Negative acting HLH proteins Id 1, Id 2, Id 3, and Id 4 are expressed in prostate epithelial cells.
BACKGROUND
The four known Id proteins, Id 1, Id 2, Id 3, and Id 4 are largely considered as dominant negative helix-loop-helix (HLH) proteins. They can dimerize with basic helix loop proteins (bHLH) but the dimers fail to bind the consensus E box response element (CANNTG). Alternatively, members of the Id family, for example, Id 2 can also bind to non-bHLH proteins such as retinoblastoma (Rb) and ETS-TCF to modulate their activities. Consistent with their role as promoters of proliferation, subset of Id genes for example, Id 1 and Id 2 are expressed in many cancers including that of the prostate. However, their expression and function in the normal prostate is unknown.


METHODS
The present study was designed to evaluate the expression profile and functional significance of all Id isoforms in normal rat prostate epithelial cells. The data suggests that all four Id isoforms are expressed in normal cells, albeit at different levels.


RESULTS
Agents that promote growth, for example, serum increase the levels of Id 1, Id 2, and Id 3. The hormones and mitogens such as testosterone and hepatocyte growth factor (HGF) that promote prostate epithelial cell differentiation stimulate Id 4 and Id 2, respectively.


CONCLUSIONS
In prostate epithelial cells, Id 1 may be specifically involved in promoting proliferation whereas Id 4 and Id 2 may have defined roles in regulating differentiated functions in response to androgens and local paracrine factors such as HGF.
Chaudhary
Jaideep
J
Center for Reproductive Biology, School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4231, USA. jaideep@wsu.edu
Schmidt
Michelle
M
Sadler-Riggleman
Ingrid
I
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D018257:Helix-Loop-Helix Motifs / Q000502:physiology*; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D008297:Male; D016376:Oligonucleotides, Antisense; D011467:Prostate / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; C497454:ID1 protein, rat; C497451:Id2 protein, rat; C499848:Id3 protein, rat; C490126:Id4 protein, rat; D051798:Inhibitor of Differentiation Protein 1; D051797:Inhibitor of Differentiation Protein 2; D051796:Inhibitor of Differentiation Proteins; D016376:Oligonucleotides, Antisense; D012097:Repressor Proteins; D014157:Transcription Factors