Human prostatic acid phosphatase, an authentic tyrosine phosphatase, dephosphorylates ErbB-2 and regulates prostate cancer cell growth.
Cellular prostatic acid phosphatase (cPAcP), an authentic tyrosine phosphatase, is proposed to function as a negative growth regulator of prostate cancer (PCa) cells in part through its dephosphorylation of ErbB-2. Nevertheless, the direct interaction between cPAcP and ErbB-2 has not been shown nor the specific dephosphorylation site of ErbB-2 by cPAcP. In this report, our data show that the phosphorylation level of ErbB-2 primarily at Tyr(1221/2) correlates with the growth rate of both LNCaP and MDA PCa2b human PCa cells. Further, cPAcP reciprocally co-immunoprecipitated with ErbB-2 in a non-permissive growth condition. Expression of wild type cPAcP, but not inactive mutant, by cDNA in cPAcP-null LNCaP C-81 cells results in decreased tyrosine phosphorylation of ErbB-2 including Tyr(1221/2). Concurrently, Tyr(317) phosphorylation of p52(Shc), proliferating cell nuclear antigen expression, and cell growth are decreased in these cells. Conversely, decreased cPAcP expression by short hairpin RNA in LNCaP C-33 cells was associated with elevated phosphorylation of ErbB-2 initially at Tyr(1221/2). Its downstream p52(Shc), ERK1/2, Akt, Src, STAT-3, and STAT-5 were activated, and cell proliferation, proliferating cell nuclear antigen, and cyclin D1 expression were increased. Stable subclones of C-33 cells by small interfering PAcP had elevated Tyr(1221/2) phosphorylation of ErbB-2 and exhibited androgen-independent growth and increased tumorigenicity in xenograft female animals. In summary, our data together indicate that in prostate epithelia, cPAcP interacts with and dephosphorylates ErbB-2 primarily at Tyr(1221/2) and hence blocks downstream signaling, leading to reduced cell growth. In PCa cells, decreased cPAcP expression is associated with androgen-independent cell proliferation and tumorigenicity as seen in advanced hormone-refractory prostate carcinomas.
Chuang
Tsai-Der
TD
Department of Biochemistry and Molecular Biology, College of Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Chen
Siu-Ju
SJ
Lin
Fen-Fen
FF
Veeramani
Suresh
S
Kumar
Satyendra
S
Batra
Surinder K
SK
Tu
Yaping
Y
Lin
Ming-Fong
MF
D000135:Acid Phosphatase; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism / Q000502:physiology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D013347:Subcellular Fractions; D014443:Tyrosine / Q000737:chemistry
D000135:Acid Phosphatase; D017027:Protein Tyrosine Phosphatases; D018719:Erb-b2 Receptor Tyrosine Kinases; D014443:Tyrosine; C428439:prostatic acid phosphatase