Abundant expression of ponsin, a focal adhesion protein, in lens and downregulation of its expression by impaired cytoskeletal signaling.
OBJECTIVE
This study was undertaken to improve understanding of the defective lens developmental changes induced by the transgenic overexpression of the Rho GDP dissociation inhibitor RhoGDIalpha. The study was focused on a single differentially expressed gene encoding ponsin, a cell adhesion interacting signaling adaptor protein.


METHODS
Total RNA extracted from the P7 lenses of Rho GDIalpha transgenic mice was subjected to cDNA microarray analysis. Ponsin distribution in the mouse lenses was determined by immunofluorescence and immunoblot analyses. Interactions among ponsin, actin, and Rho GTPase signaling pathways were explored in lens epithelial cells.


RESULTS
The RhoGDIalpha transgenic mouse lenses revealed a marked downregulation of expression of multiple splice variants of ponsin. Expression of one of the ponsins (U58883) was found to be abundant in normal mouse lenses. Although ponsin was localized predominantly to the focal adhesions in lens epithelial cells, it was distributed to both the epithelium and fibers, with some isoforms being enriched primarily in the Triton X-100-insoluble fraction in lens tissue. Further, whereas constitutively active RhoA induced ponsin clustering at the leading edges, inhibition of Rho kinase and latrunculin treatment were noted to lead to decreases in ponsin protein levels in lens epithelial cells.


CONCLUSIONS
Abundant expression of ponsin, a focal adhesion protein in the lens tissue indicates a potential role for this protein in lens fiber cell migration and adhesion. Ponsin expression appears to be closely dependent on Rho GTPase-regulated integrity of actin cytoskeletal organization.
Rao
P Vasantha
PV
Departments of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27710, USA. rao00011@mc.duke.edu
Maddala
Rupalatha
R
D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D018929:Cell Culture Techniques; D003599:Cytoskeleton / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D020869:Gene Expression Profiling; D005838:Genotype; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics; D015151:Immunoblotting; D007908:Lens, Crystalline / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D053778:Thiazolidines / Q000494:pharmacology; D014162:Transfection; D019076:Transgenes; D020741:rho GTP-Binding Proteins; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
C569639:Arhgdia protein, mouse; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D020730:Guanine Nucleotide Dissociation Inhibitors; D008840:Microfilament Proteins; D053778:Thiazolidines; C119201:ponsin; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins; C037068:latrunculin B