PTPN21-CDSlong isoform inhibits the response of acute lymphoblastic leukemia cells to NK-mediated lysis via the KIR/HLA-I axis.

Protein tyrosine phosphatase non-receptor type 21 (PTPN21) is a member of the non-receptor tyrosine phosphatase family. We have found that PTPN21 is mutated in relapsed Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation. PTPN21 consists of three types of isoforms according to the length of the protein encoded. However, the roles of different isoforms in leukemic cells have not been elucidated. In the study, PTPN21 isoform constitution in five ALL cell lines were identified by transcriptome polymerase chain reaction combined with Sanger sequencing, and the relationship between PTPN21 isoforms and sensitivity to natural killer (NK) cells mediated killing in ALL cell lines were further assessed by knock-out of different isoforms of PTPN21 using CRISPR-Cas9 technique. Subsequently, we explored the functional mechanisms through RNA sequencing and confirmatory testing. The results showed that there was no significant change when all PTPN21 isoforms were knocked out in ALL cells, but the sensitivity of NALM6 cells with PTPN21-CDSlong knock-out (NALM6-PTPN21lk ) to NK-mediated killing was significantly increased. Whole transcriptome sequencing and further validation testing showed that human leukocyte antigen class I (HLA-I) molecules were significantly decreased, accompanied by a significantly downregulated expression of antigen presenting-related chaperones in NALM6-PTPN21lk cells. Our results uncovered a previously unknown mechanism that PTPN21-CDSlong and CDSshort isoforms may play opposite roles in NK-mediated killing in ALL cells, and showed that the endogenous PTPN21-CDSlong isoform inhibited ALL cells to NK cell-mediated lysis by regulating the KIR-HLA-I axis.

Structural analysis of the FERM domain of human protein tyrosine phosphatase non-receptor type 21.

Protein tyrosine phosphatase non-receptor type 21 (PTPN21) is a cytosolic protein tyrosine phosphatase that regulates cell growth and invasion. Due to its oncogenic properties, PTPN21 has recently emerged as a potential therapeutic target for cancer. In this study, the three-dimensional structure of the PTPN21 FERM domain was determined at 2.1 Šresolution by X-ray crystallography. The crystal structure showed that this domain harbors canonical FERM folding and consists of three subdomains that are tightly packed via highly conserved intramolecular hydrophobic interactions. Consistent with this, the PTPN21 FERM domain shares high structural homology with several other FERM domains. Moreover, structural superimposition demonstrated two putative protein-binding sites of the PTPN21 FERM domain, which are presumed to be associated with interaction with its binding partner, kinesin family member 1C. Thus, these data suggest that the FERM domain of PTPN21 serves as a module that mediates protein-protein interaction, like other FERM domains.

The effect of microRNA-155 on the proliferation,invasion,migration and apoptosis of hepatocellular carcinoma cells / 介入放射学杂志

Objective To discuss the effect of PI3K-AKT signaling pathway regulated by microRNA-155(miRNA-155)targeted protein tyrosine phosphatase non-receptor type 21(PTPN21)on the proliferation,migration and invasion of hepatocellular carcinoma(HCC)cells.Methods Lentivirus transfection was used to silence the expression of miRNA-155 in human Huh7 HCC cells,and real-time fluorescent quantitative polymerase chain reaction(RT-qPCR)was used to detect the silencing effect of miR-155.After obtaining stable cell lines,the cell lines were randomly divided into Blank group(normal Huh7 cells),shNC group(Huh7 cells+empty miR-155 vector),sh-miR-155(Huh7 cells+miR-155 silencing),sh-miR-155+Recilisib group(Huh7 cells+miR-155 silencing+PI3K-AKT agonist),shNC+Recilisib group(Huh7 cells+empty miR-155 vector+PI3K-AKT agonist).Dual luciferase assay was used to determine whether PTPN21 was the downstream of miR-155.The cell proliferation ability of cells in each group was detected by MTT assay.The apoptosis level of each group was tested by flow cytometry.The invasion and migration ability of cells was assessed by Transwell assay.Western blot analysis was used to observe the differences in protein expression of PTPN21,PI3K,P-PI3K,AKT,P-AKT,and apoptosis-related proteins including BAX,BCL-2 and caspase-3 in all groups.Results The expression level of miR-155 in sh-miR-155 group was lower than that in Blank group and shNC group(P＜0.000 1),and the difference in miR-155 expression level between Blank group and shNC group was not statistically significant(P＞0.05).MTT results showed that A values of Huh7 cells at 2,3,4 and 5 day in sh-miR-155 group were lower than those in Blank group and shNC group(P＜0.000 1),while these differences between Blank group and shNC group were not statistically significant(P＞0.05).In sh-miR-155 group the A values at 2,3,4 and 5 day were lower than those in sh-miR-155+Recilisib group and shNC+Recilisib group(P=0.0052 and P＜0.0001,respectively),while the A values at 2,3,4 and 5 day in sh-miR-155+Recilisib were lower than those in shNC+Recilisib group(P＜0.000 1).There was no significant differences in cell migration and number of invasion cells between the Blank group and shNC group(P＞0.05).After activation of PI3K-AKT signaling pathway,the migration and invasion capacity of HCC cells in the shNC+Recilisib group were significantly enhanced when compared with the Blank group(P＜0.000 1).In contrast,the number of migrated and invaded Huh7 cells after miR-155 silencing was significantly lower than that in the Blank group and shNC group(P＜0.000 1)and this phenomenon became reversed by PI3K agonist.Compared with the sh-miR-155 group,in the sh-miR-155+Recilisib group the migration and invasion ability of HCC cells was enhanced(P=0.000 2).Lentiviral transfection of Huh7 human HCC cells to silence miR-155 and downregulate miR-155 inhibiting PTPN21 regulation of the PI3K-AKT signaling pathway,thus inhibiting the invasion,migration and proliferation ability of HCC cells and promoting the apoptosis of HCC cells.Conclusion miR-155 inhibits the migration,invasion and proliferation of HCC cells through targeting PTPN21 regulation of PI3K-AKT signaling pathway.The miR-155 may be a potential therapeutic target for HCC in the future.(J Intervent Radiol,2024,32:44-51)