scholarly journals Protein Tyrosine Kinase 6 Negatively Regulates Growth and Promotes Enterocyte Differentiation in the Small Intestine

2006 ◽  
Vol 26 (13) ◽  
pp. 4949-4957 ◽  
Author(s):  
Andrea Haegebarth ◽  
Wenjun Bie ◽  
Ruyan Yang ◽  
Susan E. Crawford ◽  
Valeri Vasioukhin ◽  
...  
Keyword(s):  
Small Intestine ◽  
Epithelial Cells ◽  
Tyrosine Kinase ◽  
Protein Tyrosine Kinase ◽  
Cell Types ◽  
Intestinal Epithelial ◽  
Fatty Acid Binding ◽  
Protein Tyrosine ◽  
Adult Mice ◽  
Enterocyte Differentiation

ABSTRACT Protein tyrosine kinase 6 (PTK6) (also called Brk or Sik) is an intracellular tyrosine kinase that is expressed in breast cancer and normal epithelial linings. In adult mice, PTK6 expression is high in villus epithelial cells of the small intestine. To explore functions of PTK6, we disrupted the mouse Ptk6 gene. We detected longer villi, an expanded zone of PCNA expression, and increased bromodeoxyuridine incorporation in the PTK6-deficient small intestine. Although differentiation of major epithelial cell types occurred, there was a marked delay in expression of intestinal fatty acid binding protein, suggesting a role for PTK6 in enterocyte differentiation. However, fat absorption was comparable in wild-type and Ptk6 −/− mice. It was previously shown that the serine threonine kinase Akt is a substrate of PTK6 and that PTK6-mediated phosphorylation of Akt on tyrosine resulted in inhibition of Akt activity. Consistent with these findings, we detected increased Akt activity and nuclear β-catenin in intestines of PTK6-deficient mice and decreased nuclear localization of the Akt substrate FoxO1 in villus epithelial cells. PTK6 contributes to maintenance of tissue homeostasis through negative regulation of Akt in the small intestine and is associated with cell cycle exit and differentiation in normal intestinal epithelial cells.

Role of acid/base homeostasis in the suppression of apoptosis in haemopoietic cells by v-Abl protein tyrosine kinase

1997 ◽  
Vol 110 (3) ◽  
pp. 379-387 ◽  
Author(s):  
Q. Chen ◽  
R.S. Benson ◽  
A.D. Whetton ◽  
S.R. Brant ◽  
M. Donowitz ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Intracellular Ph ◽  
Protein Tyrosine Kinase ◽  
Cell Types ◽  
Temperature Sensitive ◽  
Slight Reduction ◽  
Protein Tyrosine ◽  
Interleukin 3 ◽  
Induced Apoptosis ◽  
Acid Loading

Removal of interleukin-3 from murine IC.DP pre-mast cells results in irreversible commitment to apoptosis within 18 hours. To identify early events necessary for the engagement of apoptosis we examined the regulation of intracellular pH (pH(i)). IC.DP cells acidified 2 hours after removal of interleukin-3 (before discernible signs of apoptosis) and by 18 hours pH(i) had decreased by 0.15 units. The acidification was due to both an increase in an acid-loading process which only occurs when intracellular pH is above 6.8 and a slight reduction in H+ efflux via NA+/H+ exchange. Activation of a temperature sensitive mutant of v-Abl protein tyrosine kinase suppressed apoptosis of IC.DP cells in the absence of interleukin-3 but did not stimulate proliferation, and moreover prevented cellular acidification. Acidification of the cells by 0.2 units to pH 6.86 by complete inhibition of Na+/H+ exchange by 10 microM 5′-(N-methyl-N-isobutyl)-amiloride prevented the suppression of apoptosis by v-abl protein tyrosine kinase following IL 3 withdrawal. However in the presence of interleukin-3, addition of 10 microM 5′-(N-methyl-N-isobutyl)-amiloride only resulted in a fall of pH(i) to 7.17. Apoptosis did not occur and the cells continued to proliferate. Thus, in this model intracellular pH must fall below a critical value for apoptosis to occur. Together these data point to a step in cytokine deprivation induced apoptosis (at least in some haemopoietic cell types) which is either enhanced by or dependent upon an acidic intracellular environment which is the result of an increase in acid loading and inhibition of Na+/H+ exchange activity. One of the mechanisms by which activation of v-Abl protein tyrosine kinase suppresses apoptosis is by prevention of intracellular acidification.

scholarly journals Induction of Protein Tyrosine Kinase 6 in Mouse Intestinal Crypt Epithelial Cells Promotes DNA Damage–Induced Apoptosis

2009 ◽  
Vol 137 (3) ◽  
pp. 945-954 ◽  
Author(s):  
Andrea Haegebarth ◽  
Ansu O. Perekatt ◽  
Wenjun Bie ◽  
Jessica J. Gierut ◽  
Angela L. Tyner
Keyword(s):  
Dna Damage ◽  
Epithelial Cells ◽  
Tyrosine Kinase ◽  
Protein Tyrosine Kinase ◽  
Intestinal Crypt ◽  
Protein Tyrosine ◽  
Induced Apoptosis

Radiation inactivation and in situ renaturation of protein tyrosine kinases reveal a major 50-kDa enzyme as part of a membrane complex present in dividing but not in resting prostatic epithelial cells

1996 ◽  
Vol 74 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Linh The Nguyen ◽  
Yves Durocher ◽  
Guy Beauregard ◽  
Sylvain Tessier ◽  
Azeddine Atfi ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Protein Tyrosine Kinase ◽  
Specific Activity ◽  
Protein Tyrosine Kinases ◽  
Radiation Inactivation ◽  
Protein Tyrosine ◽  
Dividing Cells ◽  
Membrane Bound

Because protein tyrosine kinases play a crucial role in the regulation of cell division and carcinogenesis, we have herein measured such enzyme activities (specific activity and subcellular distribution) and compared their characteristics with respect to hydrodynamic properties and radiation inactivation sizes as well as renaturation after electrophoresis in denaturing conditions in canine prostatic epithelial cells either in a resting (freshly isolated) or in a dividing (cultured cells) state. In quiescent cells, most protein tyrosine kinase activity was expressed by soluble proteins with a Stokes' radius (Rs) of 3.05 nm, a sedimentation coefficient (S20,w) of 4.0 S, and a molecular mass of 50 kDa. By contrast, in dividing cells (three days in primary culture), the specific activity was higher and the enzyme was mainly membrane bound. The use of a detergent (Triton X-100) allowed the extraction of most of that enzyme; its partial specific volume, S20,w, and Rs were then 0.883 cm3/g, 4.0 S, and 5.6 nm, respectively, hence yielding a molecular mass of 215 kDa, which decreased to 125–145 kDa when corrected for detergent binding. Probing these chromatography-peak fractions, 50 kDa from cytosol of resting cells and 215 kDa from membrane extracts of dividing cells, with a phosphotyrosine antibody following their incubation with ATP and electrophoresis in denaturing conditions revealed the presence of a common 50-kDa phosphotyrosylated protein along with three other bands (130, 75, and 40 kDa) in the high-Mr peak of enzyme. However, the radiation inactivation size for protein tyrosine kinases expressed in both resting and dividing cells were similar, 47.2 ± 8.7 and 44.5 ± 6.1 kDa, respectively. Furthermore, by renaturation after electrophoresis in denaturing conditions, major protein tyrosine kinase polypeptides of 50 kDa were identified in both cell populations. Taken together, these results indicate that, in dividing prostatic epithelial cells, membrane-bound protein tyrosine kinases of low molecular weight with properties similar to those of monomeric soluble forms present in quiescent cells are part of high-molecular weight complexes. This activation process may be critical for hormone-independent proliferation of prostatic epithelial cells.Key words: protein tyrosine kinase, kinase renaturation, cell division, prostate, radiation inactivation.

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