scholarly journals Regulation of Phosphoinositide Levels in the Retina by Protein Tyrosine Phosphatase 1B and Growth Factor Receptor-Bound Protein 14

Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 602
Author(s):  
Raju V. S. Rajala ◽  
Austin McCauley ◽  
Rahul Rajala ◽  
Kenneth Teel ◽  
Ammaji Rajala
Keyword(s):  
Growth Factor ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Kinases ◽  
Knockout Mouse ◽  
Tyrosine Phosphatase ◽  
Growth Factor Receptor ◽  
Mouse Retina ◽  
Protein Tyrosine Phosphatase 1B ◽  
Protein Tyrosine ◽  
Growth Factor Receptor Bound

Protein tyrosine kinases and protein phosphatases play a critical role in cellular regulation. The length of a cellular response depends on the interplay between activating protein kinases and deactivating protein phosphatases. Protein tyrosine phosphatase 1B (PTP1B) and growth factor receptor-bound protein 14 (Grb14) are negative regulators of receptor tyrosine kinases. However, in the retina, we have previously shown that PTP1B inactivates insulin receptor signaling, whereas phosphorylated Grb14 inhibits PTP1B activity. In silico docking of phosphorylated Grb14 and PTP1B indicate critical residues in PTP1B that may mediate the interaction. Phosphoinositides (PIPs) are acidic lipids and minor constituents in the cell that play an important role in cellular processes. Their levels are regulated by growth factor signaling. Using phosphoinositide binding protein probes, we observed increased levels of PI(3)P, PI(4)P, PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 in PTP1B knockout mouse retina and decreased levels of these PIPs in Grb14 knockout mouse retina. These observations suggest that the interplay between PTP1B and Grb14 can regulate PIP metabolism.

Protein tyrosine phosphatase activity in human endometrium

2001 ◽  
Vol 13 (3) ◽  
pp. 175 ◽  
Author(s):  
Seppo Partanen
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Phosphatase Activity ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Kinases ◽  
Tyrosine Phosphatase ◽  
Intrauterine Device ◽  
Human Endometrium ◽  
Protein Tyrosine ◽  
Glandular Cells

Protein tyrosine phosphatase (PTP) activity was demonstrated in human endometrium by a histochemical method using phosphotyrosine as substrate. For comparative purposes, non-specific acid phosphatase (AcP) activity was also examined. Protein tyrosine phosphatase activity was very low in proliferative and atrophic endometrium, but its activity was increased 9-fold in glandular epithelium during the secretory phase, and 48-fold in predecidual endometrium, induced by a progestagen-releasing intrauterine device, compared with the proliferative endometrium. Thus, PTP activity appeared to be progesterone-induced. Endometrial PTP appeared to be cellular rather than secretory in origin; its activity was inhibited by vanadate, and its histochemical properties were different from those of lysosomal AcP, but similar to those of prostatic-type AcP. Endometrial PTP may functionally counteract the effects of protein tyrosine kinases (PTKs) associated with growth factor receptors and cellular oncoproteins. Cyclic endometrial proliferation and differentiation are thought to be regulated by the autocrine and paracrine pathways by growth factors such as epidermal growth factor, insulin-like growth factor I and platelet-derived growth factors, and their receptors. However, cessation of proliferation could not be explained by the amounts of these growth factors present or their receptors, in that no constant changes at the interface of the late proliferative and early secretory phases were found. Down-regulation of stimulatory-signalling pathways of PTKs by endometrial PTP induced by progesterone may explain the decrease observed in proliferative activity of glandular cells in cyclic endometrium.

Sign in / Sign up

Export Citation Format

Share Document