Regulation of the Src kinase-associated phosphoprotein 55 homologue by the protein tyrosine phosphatase PTP-PEST in the control of cell motility.

PTP-PEST is a cytosolic ubiquitous protein tyrosine phosphatase (PTP) that contains, in addition to its catalytic domain, several protein-protein interaction domains that allow it to interface with several signaling pathways. Among others, PTP-PEST is a key regulator of cellular motility and cytoskeleton dynamics. The complexity of the PTP-PEST interactome underscores the necessity to identify its interacting partners and physiological substrates in order to further understand its role in focal adhesion complex turnover and actin organization. Using a modified yeast substrate trapping two-hybrid system, we identified a cytosolic adaptor protein named Src kinase-associated phosphoprotein 55 homologue (SKAP-Hom) as a novel substrate of PTP-PEST. To confirm PTP-PEST interaction with SKAP-Hom, in vitro pull down assays were performed demonstrating that the PTP catalytic domain and Proline-rich 1 (P1) domain are respectively binding to the SKAP-Hom Y260 and Y297 residues and its SH3 domain. Subsequently, we generated and rescued SKAP-Hom-deficient mouse embryonic fibroblasts (MEFs) with WT SKAP-Hom, SKAP-Hom tyrosine mutants (Y260F, Y260F/Y297F), or SKAP-Hom SH3 domain mutant (W335K). Given the role of PTP-PEST, wound-healing and trans-well migration assays were performed using the generated lines. Indeed, SKAP-Hom-deficient MEFs showed a defect in migration compared with WT-rescued MEFs. Interestingly, the SH3 domain mutant-rescued MEFs showed an enhanced cell migration corresponding potentially with higher tyrosine phosphorylation levels of SKAP-Hom. These findings suggest a novel role of SKAP-Hom and its phosphorylation in the regulation of cellular motility. Moreover, these results open new avenues by which PTP-PEST regulates cellular migration, a hallmark of metastasis.

The World Federation of Hemophilia World Bleeding Disorders Registry: insights from the first 10,000 patients.

Background: The prevalence of hemophilia varies globally, with close to 100% of patients diagnosed in high-income countries and as low as 12% diagnosed in lower-income countries. These inequalities in the care of people with hemophilia exist across various care indicators. Objectives: This analysis aims to describe the clinical care outcomes of patients in the World Bleeding Disorders Registry (WBDR). Methods: In 2018, the World Federation of Hemophilia developed a global registry, the WBDR, to permit hemophilia treatment centers to collect clinical data, monitor patient care longitudinally, and identify gaps in management and treatment. Results: As of July 18, 2022, 10,276 people with hemophilia were enrolled from 87 hemophilia treatment centers in 40 countries. Nearly half (49%, n = 5084) of patients had severe hemophilia; 99% were male, 85% had hemophilia A, and 67% were from low-middle-income countries. Globally, the age of diagnosis for people with severe hemophilia has improved considerably over the last 50 years, from 82 months (∼7 years) for those born before 1980 to 11 months for those born after 2010, and most prominently, among people with severe hemophilia in low- and low-middle-income countries, the age of diagnosis improved from 418 months (∼35 years) for those born before 1970 to 12 months for those born after 2010. Overall, the age of diagnosis of people with hemophilia in low- and low-middle-income countries is delayed by 3 decades compared to patients in upper-middle-income countries and by 4 decades compared to patients in high-income countries. Conclusion: Data reveal large treatment and care disparities between socioeconomic groups, showing improvements when prophylaxis is initiated to prevent bleeding. Overall, care provided in low-income countries lags behind high-income countries by up to 40 years. Limitations in the interpretation of data include risk of survival and selection bias.

Functional variants of human APE1 rescue the DNA repair defects of the yeast AP endonuclease/3'-diesterase-deficient strain.

Human APE1 is an essential enzyme performing functions in DNA repair and transcription. It possesses four distinct repair activities acting on a variety of base and sugar derived DNA lesions. APE1 has seven cysteine residues and Cys65, and to a lesser extent Cys93 and Cys99, is uniquely involved in maintaining a subset of transcription factors in the reduced and active state. Four of the cysteines Cys93, 99, 208 and 310 of APE1 are located proximal to its active site residues Glu96, Asp210 and His309 involved in processing damaged DNA, raising the possibility that missense mutation of these cysteines could alter the enzyme DNA repair functions. An earlier report documented that serine substitution of the individual cysteine residues did not affect APE1 ability to cleave an abasic site oligonucleotide substrate in vitro, except for Cys99Ser, although any consequences of these variants in the repair of in vivo DNA lesions were not tested. Herein, we mutated all seven cysteines of APE1, either singly or in combination, to alanine and show that none of the resulting variants interfered with the enzyme DNA repair functions. Cross-specie complementation analysis reveals that these APE1 cysteine variants fully rescued the yeast DNA repair deficient strain YW778, lacking AP endonucleases and 3'-diesterases, from toxicities caused by DNA damaging agents. Moreover, the elevated spontaneous mutations arising in strain YW778 from the lack of the DNA repair activities were completely suppressed by the APE1 cysteine variants. These findings suggest that the cysteine residues of APE1 are unlikely to play a role in the DNA repair functions of the enzyme in vivo. We also examine other APE1 missense mutations and provide the first evidence that the variant Asp308Ala with normal AP endonuclease, but devoid of 3'→5' exonuclease, displays hypersensitivity to the anticancer drug bleomycin, and not to other agents, suggesting that it has a defect in processing unique DNA lesions. Molecular modeling reveals that Asp308Ala cannot make proper contact with Mg(2+) and may alter the enzyme ability to cleave or disassociate from specific DNA lesions.