Protein tyrosine phosphatases PTP-1B and TC-PTPplay nonredundant roles in macrophage developmentand IFN-� signalingKrista M. Heinonena,b,1, Annie Bourdeaub,1, Karen M. Doodyb,c,1, and Michel L. Tremblaya,b,c,2

aDivision of Experimental Medicine, bGoodman Cancer Centre, and cDepartment of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada

Edited by Arthur Weiss, University of California, San Francisco, CA, and approved April 21, 2009 (received for review November 27, 2008)

The control of tyrosine phosphorylation depends on the finebalance between kinase and phosphatase activities. Proteintyrosine phosphatase 1B (PTP-1B) and T cell protein tyrosinephosphatase (TC-PTP) are 2 closely related phosphatases knownto control cytokine signaling. We studied the functional redun-dancy of PTP-1B and TC-PTP by deleting 1 or both copies of thesegenes by interbreeding TC-PTP and PTP-1B parental lines. Ourresults indicate that the double mutant (tcptp�/�ptp1b�/�) islethal at day E9.5–10.5 of embryonic development with consti-tutive phosphorylation of Stat1. Mice heterozygous for TC-PTPon a PTP-1B– deficient background (tcptp�/�ptp1b�/�) devel-oped signs of inflammation. Macrophages from these animalswere highly sensitive to IFN-�, as demonstrated by increasedStat1 phosphorylation and nitric oxide production. In addition,splenic T cells demonstrated increased IFN-� secretion capacity.Mice with deletions of single copies of TC-PTP and PTP-1B(tcptp�/�ptp1b�/�) exhibited normal development, confirmingthat these genes are not interchangeable. Together, these dataindicate a nonredundant role for PTP-1B and TC-PTP in theregulation of IFN signaling.

immune system � interferon gamma � lymphocyte development �protein tyrosine phosphatase

T cell protein tyrosine phosphatase (TC-PTP; also known asPTPN2) and protein tyrosine phosphatase 1B (PTP-1B; also

known as PTPN1) are intracellular phosphatases with a highdegree of sequence and structural homology within the catalyticdomain (1, 2). PTP-1B is known to dephosphorylate the insulinreceptor (3, 4), and ptp1b�/� mice are protected from diet-induced insulin-resistance and obesity (3, 5, 6). This phenotypehas incited much interest in PTP-1B inhibitors in treating typeII diabetes (7, 8). However, because of the structural homologywith TC-PTP, none of the small-molecule inhibitors developedto date exhibits a high degree of selectivity against PTP-1B, andonly a few are currently in clinical trials.

Both TC-PTP and PTP-1B have been shown to modulatecytokine receptor signaling (reviewed in ref. 9), including IFN-�signaling (10, 11). IFN-� is a major inflammatory cytokine, andligation of the IFN-� receptor results in the activation ofcytoplasmic Jak1 and Jak2 kinases as well as the transcriptionfactor Stat1 (12). Jak1 and Stat1 are known substrates ofTC-PTP (11, 13), whereas Jak2 is known to be dephosphorylatedby PTP-1B (10). Consequently, we hypothesized that the dele-tion of both TC-PTP and PTP-1B would exacerbate the inflam-matory phenotype seen in tcptp�/� mice (14, 15).

The data presented here indicate that at least 1 copy of tcptpor ptp1b is required for normal embryonic development. Ourresults show that the sequential ablation of TC-PTP and PTP-1Breveals a thus-far undetected gene dosage effect. This suggeststhat small-molecule inhibitors against PTP-1B that also inhibitTC-PTP may have multilevel effects that are proportional to thenet reduction in both TC-PTP and PTP-1B activity.

ResultsThe tcptp�/�ptp1b�/� Double Mutant Is Lethal During EmbryonicDevelopment. To study the redundancy of TC-PTP and PTP-1Bfunction in vivo, we obtained tcptp�/�ptp1b�/� double-deficientmice. Using tcptp�/�ptp1b�/� mice as breeders, we obtained nodouble mutants at 3–5 days of age (Table 1), suggesting that theloss of both TC-PTP and PTP-1B resulted in embryonic death.

Examination of embryos revealed no obvious embryonic,placental, or yolk sac abnormalities and a normal Mendelianratio in E8.5–9.0 live embryos generated from tcptp�/�ptp1b�/�

intercrosses (Fig. 1A). At E9.5–10.5, the tcptp�/�ptp1b�/� em-bryos showed signs of growth retardation, including a smallerhead and underdeveloped nasal processes and branchial arches.The heart was still beating (Fig. 1B). At E11.5, most of thetcptp�/�ptp1b�/� embryos were dead, with collapsed vasculatureand tissue necrosis. No tcptp�/�ptp1b�/� individuals were de-tected past E12 (Fig. 1 A). We assessed the relative proportionof progenitor cells (CD117�Ter119�), CD117�Ter119� ery-throid cells, CD117loTer119lo erythroid precursor cells, CD309�

(Flk-1 or VEGFR2) endothelial cells, and CD11b� macrophagesby flow cytometry in E10–10.5 yolk sacs. As shown in supportinginformation (SI) Fig. S1, the absence of tcptp and ptp1b in yolksacs did not affect a specific cell lineage, but rather impedednormal embryonic development.

To further characterize the early lethality of tcptp�/�ptp1b�/�

embryos, we analyzed whole-protein lysates prepared fromE9.5–10.5 embryos for differences in protein expression. Stat1 isa substrate of TC-PTP (16) that can lead to apoptosis orattenuate cytokines essential for embryonic development (17,18). Strong Stat1 phosphorylation levels were detected intcptp�/� ptp1b�/� embryos at E9.5–10.5; however, no Stat1phosphorylation was evident in any other genotype (Fig. 2;tcptp�/� ptp1b�/� not shown). In addition, a small increase inStat1 protein level also was seen in the tcptp�/� ptp1b�/�

embryos compared with their littermates (Fig. 2). These resultssuggest a complementary role of TC-PTP and PTP-1B in Stat1regulation. In contrast, Stat3 and Stat5 phosphorylation variedbetween individuals, possibly due to differential regulationduring development, and no conclusive hyperphosphorylationwas detected in the tcptp�/� ptp1b�/� embryos compared withtheir littermates (Fig. S2).

Haploinsufficiency of tc-ptp Becomes Apparent on ptp1b�/� Back-ground. Both tcptp�/� and ptp1b�/� mice have essentially normallife spans and are fertile; however, when put on a ptp1b�/�

Author contributions: K.M.H., A.B., K.M.D., and M.L.T. designed research; K.M.H., A.B., andK.M.D. performed research; K.M.H., A.B., and K.M.D. analyzed data; and K.M.H., A.B.,K.M.D., and M.L.T. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

1K.M.H., A.B., and K.M.D. contributed equally to this work.

2To whom correspondence should be addressed. E-mail: michel.tremblay@mcgill.ca.

This article contains supporting information online at www.pnas.org/cgi/content/full/0812109106/DCSupplemental.

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background, more than half of tcptp�/� ptp1b�/� mice die by age3 months (Fig. 3A), and the remaining mice do not survive past9 months (data not shown). Conversely, tcptp�/� ptp1b�/� miceare fertile, present no evident abnormalities, and survive past 12months.

Young tcptp�/� ptp1b�/� mice (age 5–6 weeks) were smallerthan their littermates and, on examination of the majorhematopoietic cell types in the bone marrow, displayed de-creased numbers of Ter119hi mature and immature erythroidcells, suggesting that they may have been anemic (Fig. 3B),similar to tcptp�/� mice (15). In comparison, the numbers ofCD11b� myeloid cells and B220� B lymphocytes were normal(Fig. S3), and there was no disproportionate increase inperipheral B220�IgM�/loCD24�/lo cells (Fig. S4) that wouldcharacterize chronically activated follicular type B cells. Oldertcptp�/� ptp1b�/� mice had lower body weight and exhibitedsignificant splenomegaly, lymphadenopathy, and acceleratedthymic atrophy, as well as massive mononuclear infiltrates tothe lacrimal and salivary glands and the gastric mucosa (TableS1 and data not shown), whereas age-matched heterozygoustcptp�/� ptp1b�/� and tcptp�/� ptp1b�/� controls were mostly

normal. It is also noteworthy that tcptp�/� ptp1b�/� mice hada significantly shorter lifespan than tcptp�/� ptp1b�/� mice(mean survival, 20.4 � 1.7 days vs. 25.3 � 3.5 days; P � .0001)and that the incidence of live tcptp�/� ptp1b�/� births wassomewhat lower than expected (Table 1).

TC-PTP and PTP-1B Collaborate in Macrophage Development. Giventhe appearance of the tcptp�/� ptp1b�/� mice, which resembledthat of tcptp�/� mice to some extent (14–16), as well as thecurrent evidence of a role for both TC-PTP and PTP-1B in thecontrol of CSF-1 (19, 20) and IFN-� signaling (10, 11), we

Fig. 1. Combined deficiency in TC-PTP and PTP-1B is lethal in early embryonicdevelopment. (A) Frequencies and expected frequencies of live tcptp�/�

ptp1b�/� embryos obtained from tcptp�/� ptp1b�/�� tcptp�/� ptp1b�/�

breeders at E9.5–13.5 postcoitum. (B) An E10.5 tcptp�/� ptp1b�/� embryotogether with a tcptp�/� ptp1b�/� littermate.

Fig. 2. Constitutive Stat1 phosphorylation in tcptp�/� ptp1b�/� embryos.Two representative Western blots, showing hyperphosphorylation of Stat1 inE10.5 tcptp�/� ptp1b�/� embryos and no phosphorylation in either tcptp�/�

ptp1b�/� or tcptp�/� ptp1b�/� littermates. Similar results were obtained from4 different tcptp�/� ptp1b�/� embryos.

Fig. 3. Haploinsufficiency of tc-ptp is apparent on the ptp1b�/� background.(A) Survival curve of tcptp�/� ptp1b�/� mice compared with tcptp�/� ptp1b�/�

and tcptp�/� ptp1b�/�, tcptp�/� ptp1b�/�, tcptp�/� ptp1b�/� mice. (B) Per-centage and absolute number of Ter119� erythroid cells in the bone marrowof young (5- to 6-week-old) mice. The y-axes of the flow cytometry plots havebeen adjusted to show equal numbers of events. n � 6–9 per genotype. *, P �.05; **, P � .005.

Table 1. Genotype distribution in the progeny fromheterozygous matings

Genotype(tc-ptp ptp-1b) Obtained ratio Expected ratio

�/� �/� 0.053 0.063�/� �/� 0.149 0.125�/� �/� 0.062 0.063�/- �/� 0.166 0.125�/- �/- 0.280 0.250�/- �/� 0.135 0.125�/� �/� 0.068 0.063�/� �/� 0.087 0.125�/� �/� 0 0.063

Pups were identified and a piece of tail was obtained for genotyping at 3–5days after birth. The observed frequencies are on the left and the expectedMendelian frequencies on the right. n � 483. �2 � 1 � 10�6.

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hypothesized that tcptp�/� ptp1b�/� mice might exhibit defectivemacrophage development and activation.

Tcptp�/� ptp1b�/� and tcptp�/� ptp1b�/� mice both had alarger percentage of splenic CD11b�Ly6G�/lo macrophagescompared with tcptp�/� ptp1b�/� controls (Fig. 4A, Left). Takinginto account the significant splenomegaly in the tcptp�/�

ptp1b�/� mice (256 � 106 � 28 � 106 cells/spleen vs. 171 � 106 �14.2 � 106 for tcptp�/� ptp1b�/� and 103 � 106 � 10.6 � 106 fortcptp�/� ptp1b�/�; P � .02 for both), the total number ofmacrophages in tcptp�/� ptp1b�/� spleen was approximatelydouble that in tcptp�/� ptp1b�/� spleen and more than triple thatin normal mice spleen (Fig. 4A, Right).

To explain this increase in splenic macrophages, we found nosignificant increase in the total number of myeloid precursorsfrom tcptp�/� ptp1b�/� bone marrow in a mixed-colony assay(Fig. S3). In accordance with previous reports (20), tcptp�/�

ptp1b�/� bone marrow produced more colonies in the presenceof CSF-1 than control bone marrow; however, tcptp�/�

ptp1b�/� mice had even more CSF-1–responsive cells thantcptp�/� ptp1b�/� mice (Fig. 4B). This finding was specific toCSF-1; stimulation with GM-CSF did not produce any differ-ences in the number of colonies independent of genotype (Fig.4B). Our results indicate that the ability to produce CSF-1�responsive colonies does not depend solely on the fre-quency of monocyte-committed progenitors and demonstratethat TC-PTP and PTP-1B are not redundant in CSF-1 signal-ing (19, 20), but play a cooperative role in macrophagedevelopment.

Given that both TC-PTP and PTP1B are known to regulatethe IFN-� signaling pathway (10, 11, 13), we examined the IFN-�responsiveness of tcptp�/� ptp1b�/� spleen-derived macro-phages. Macrophages derived from tcptp�/� ptp1b�/� spleensproduced on average 3 times more NO than those derived fromtcptp�/� ptp1b�/� control spleens and approximately twice asmuch as those derived from either tcptp�/� ptp1b�/� or tcptp�/�

ptp1b�/� spleens (Fig. S5). Furthermore, compared with tcptp�/�

ptp1b�/� and tcptp�/� ptp1b�/� mice, Stat1 phosphorylation wassignificantly enhanced in macrophages derived from tcptp�/�

ptp1b�/� mice (Fig. 4C), indicating that TC-PTP and PTP-1Bcollaborate in the regulation of the IFN-� response directlydownstream of the receptor.

Thymic Defect in the tcptp�/�ptp1b�/� Mice. Previous data haveshown that tcptp�/� mice have normal numbers of peripheral Tcells, which do not proliferate in response to mitogenic stimuli(15) but produce large amounts of IFN-� (14). There is noreported T-cell phenotype in ptp1b�/� mice (21). Given theaccelerated thymic atrophy in tcptp�/� ptp1b�/� mice, we studiedtheir T-cell development and function in greater detail.

We found an age-dependent decrease in CD4�CD8� double-positive thymocytes in the tcptp�/� ptp1b�/� mice compared withviable littermate controls (Fig. 5A). These results suggest anearly delay in thymocyte development, and an accumulation ofcells was detected at the CD44�CD25� population (DN1 stage)in the tcptp�/� ptp1b�/� mice compared with viable littermatecontrols (Fig. 5B). Investigation of the early thymic progenitor(ETP) population and the CD117�/lo DN1 fractions (DN1c, d, e)(22) revealed a relative increase in the proportion of thecanonical CD117hi ETP (Lin�CD117hiCD25�; Fig. 5C), as wellas a more pronounced increase in noncanonical CD117�/lo

CD127� fractions with low proliferation capacity (DN1c, d/e;Fig. 5C). In addition, we detected a significant proportion ofB220� cells in the tcptp�/� ptp1b�/� thymuses, a population thatwas absent from both normal (data not shown) and tcptp�/�

ptp1b�/� thymuses (Fig. S6). Our results reflect the possibilitythat the tcptp�/� ptp1b�/� ETP and DN3 do not receive sufficientsignals for expansion and differentiation, leading to the thymicdefect and the development of B220� cells from noncanonicalprecursors.

The tcptp�/� ptp1b�/� mice exhibited elevated levels of circu-lating IFN-� shortly before death (14). In addition, their splenicT cells produced more IFN-� on a per-cell basis after mitogenicstimulation. We did not detect any serum IFN-� in unstimulatedtcptp�/� ptp1b�/� mice, but we did note the capacity of tcptp�/�

ptp1b�/� T cells to produce IFN-� in culture. IFN-� productionby control splenocytes (tcptp�/� ptp1b�/�, tcptp�/� ptp1b�/�,tcptp�/� ptp1b�/�) was essentially equal, whereas tcptp�/�

ptp1b�/� T cells produced almost twice as much IFN-� whennormalized to DNA synthesis (Fig. 5D). Our results indicate thatT cells from tcptp�/� ptp1b�/� mice have an increased capacityto produce IFN-� and thus likely contribute to the decreasedsurvival of these animals.

DiscussionThe results presented here demonstrate that TC-PTP andPTP-1B play cooperative and nonredundant roles during em-bryonic development as well as in postnatal macrophage and Tlymphocyte development and activation. The removal of 1 copyof tcptp on a ptp1b�/� background revealed a gene dosage effectthat had previously gone undetected in tcptp�/� mice. In thesetcptp�/� ptp1b�/� mice, we were able to observe the collaborativeeffect of the 2 enzymes in macrophage development both in vivoand in culture with CSF-1. This occurred at different levels;TC-PTP appears to control only dephosphorylation of thereceptor (19), whereas PTP-1B may play a role in receptorrecycling as well (20). Such a role for PTP-1B in receptor

Fig. 4. Collaborative regulation of monocyte/macrophage developmentand the macrophage IFN-� response. (A) Representative FACS data from thespleens of young (5-to 6-week-old) mice, showing the percentages ofCD11b�Ly6G�/lo monocytes and CD11b�Ly6Ghi granulocytes. n � 6–10 pergenotype. *, P � .05; **, P � .01 compared with all other genotypes unlessspecified otherwise. (B) Myeloid colony formation in methylcellulose fromtotal bone marrow from young (5- to 6-week-old) mice in response to GM-CSFand CSF-1. n � 4–6 per genotype. *, P � .05; **, P � .01. (C) RepresentativeWestern blot showing phosphorylation of Stat1 in spleen-derived macro-phages after 15 min of stimulation with 100 U/mL of IFN-�. Similar results wereobtained from 3 separate experiments.

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maturation has been proposed in the context of Flt3, anothermember of the receptor tyrosine kinase class III family (23). Ourdata also demonstrate that IFN-� signaling is potentiated intcptp�/� ptp1b�/� macrophages, and that peripheral T cells fromthese mice can secrete more IFN-� compared with cells from eithertcptp�/� ptp1b�/� or tcptp�/� ptp1b�/� mice. The normal phenotypeseen in tcptp�/� ptp1b�/� mice further suggests that TC-PTP andPTP-1B are not interchangeable enzymes and can act either ondifferent pathways or different areas of the same pathway.

IFN-� signaling requires Jak1 and Jak2 and Stat1 (12, 24,25). Stat1 and Jak1 are substrates for TC-PTP (11, 13),whereas Jak2 is dephosphorylated by PTP-1B (10). Our resultsdemonstrate that TC-PTP and PTP-1B also are not redundant

or interchangeable in the control of IFN-� signaling and Stat1phosphorylation. Macrophages from tcptp�/� ptp1b�/� spleenswere more sensitive to IFN-� than those from either tcptp�/�

ptp1b�/� or tcptp�/� ptp1b�/� control spleens; furthermore,unlike their littermates, tcptp�/� ptp1b�/� embryos exhibitedconstitutive Stat1 phosphorylation. The ablation of othernegative regulators of IFN-� signaling, SOCS1 and PIAS1, alsoresults in decreased survival (26–28). In parallel, increasingIFN-� leads to autoimmune inf lammation (29–32). Althoughthe precise cause of embryonic lethality in tcptp�/� ptp1b�/�

mice remains unknown, Stat1 activation can lead to apoptosisor inf luence the secretion of cytokines important for themigration of cells and maintenance of the embryo (17, 18).Interestingly, Stat5 and Stat3 were not significantly hyper-phosphorylated in tcptp�/� ptp1b�/� embryos, further support-ing the likely biological significance of Stat1 activation. Fur-thermore, TC-PTP and PTP-1B have multiple substrates withthe ability to affect the entire organism, including CSF1R,which likely contribute to the phenotype observed in tcptp�/�

ptp1b�/� adult mice.We also detected decreased numbers of mature and immature

Ter119� erythrocytes in young tcptp�/� ptp1b�/� animals, whichwere present in close to normal numbers in older tcptp�/�

ptp1b�/� mice that survived past 10 weeks. Because excessive IFNand Stat1 signaling can result in anemia (33, 34), we propose thatthis discrepancy may have been due to the mixed genetic back-ground, and that the mice that survived longer could have producedless IFN-� or had a slightly different response to IFN-�. (Signalingstudies were conducted on cells from young animals.)

Interferons are currently used for treatment of variouscancers, as well as hepatitis and multiple sclerosis (35). In thecase of chronic myelogenous leukemia, a negative correlationbetween responsiveness to IFN-� and TC-PTP activity hasbeen shown (36, 37). Furthermore, Stat1 is a known tumorsuppressor (38), and increasing Stat1 activity could reducetumor load and metastasis. Because the development ofTC-PTP or PTP-1B–specific inhibitors is difficult because oftheir significant homology, blocking agents with overlappingcapabilities to inhibit both enzymes may provide a usefuladvantage. Moreover, because tcptp�/� ptp1b�/� mice displayno overt abnormalities, and because ptp1b�/� mice also dem-onstrate improved glycemia in type II diabetes (3, 5, 6),reduced obesity (3, 5, 6), and delayed breast tumor develop-ment in ErbB2 transgenic models (39), we believe that the useof nonspecific PTP inhibitors against TC-PTP/PTP1B will stillhave a beneficial effect in these 3 diseases without major sideeffects, as long as sufficient amounts of both of these enzymesremain active.

Materials and MethodsMice. ptp1b�/� mice were bred with tcptp�/� mice to obtain tcptp�/�ptp1b�/�

mice, which were then interbred to obtain all of the different genotypesstudied. Genotyping was done as described previously (3, 15). All mice werekept in specific pathogen-free housing in the animal care facility. Protocolswere approved by the McGill Animal Care Ethics Committee.

Statistical Analysis. All histograms represent mean � SEM. P values weredetermined using a 2-tailed unpaired Student t test.

More details are provided in SI Materials and Methods.

ACKNOWLEDGMENTS. We thank Emily-Kate Higgins, Rosemary Siegrist-Johnstone, and Ailsa Lee Loy for their excellent technical assistance, as well asKen McDonald for his valuable help with the flow cytometry. This work wassupported by operating grants from the Canadian Institutes of Health Re-search (MOP-62887, to M.L.T.) and the National Cancer Institute of Canada(015200, to M.L.T.). K.M.H was supported by a Canada Graduate ScholarshipDoctoral Award from the Canadian Institutes of Health Research. A.B. issupported by the US Lymphoma Foundation. K.M.D. was supported by a Fondsde la recherche en sante du Quebec doctoral award. M.L.T. is a recipient of theJeanne and Jean-Louis Levesque Chair in Cancer Research.

Fig. 5. Age-dependent defect in thymic output and enhanced IFN-� secre-tion by peripheral T cells from tcptp�/� ptp1b�/� mice. (A) Representative flowcytometry plots showing a relative increase in mature single-positive thymo-cytes and a decrease in double-positive thymocytes in tcptp�/� ptp1b�/� mice.n � 5–12 per genotype. (B) Representative flow cytometry plots showing arelative increase in the DN1 subpopulation in tcptp�/� ptp1b�/� thymuses. n �5–12 per genotype. (C) Representative FACS data showing CD117 and CD127staining on lineage-negative cells in thymuses from 13- to 15-week-old mice.n � 6–10 per genotype. (D) IFN-� production by splenic CD90� cells in thesupernatant after 48 h of culture on CD3/CD28. Histograms represent mean �SEM from 3 separate experiments. *, P � .05, tcptp�/� ptp1b�/� compared withall other genotypes.

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1. Asante-Appiah E, et al. (2001) The YRD motif is a major determinant of substrate andinhibitor specificity in T-cell protein-tyrosine phosphatase. J Biol Chem 276:26036–26043.

2. Jia Z, Barford D, Flint AJ, Tonks NK (1995) Structural basis for phosphotyrosine peptiderecognition by protein tyrosine phosphatase 1B. Science 268:1754–1758.

3. Elchebly M, et al. (1999) Increased insulin sensitivity and obesity resistance in micelacking the protein tyrosine phosphatase-1B gene. Science 283:1544–1548.

4. Klaman LD, et al. (2000) Increased energy expenditure, decreased adiposity, andtissue-specific insulin sensitivity in protein-tyrosine phosphatase 1B–deficient mice.Mol Cell Biol 20:5479–5489.

5. Cheng A, et al. (2002) Attenuation of leptin action and regulation of obesity by proteintyrosine phosphatase 1B. Dev Cell 2:497–503.

6. Zabolotny JM, et al. (2002) PTP1B regulates leptin signal transduction in vivo. Dev Cell2:489–495.

7. Bento JL, et al. (2004) Association of protein tyrosine phosphatase 1B gene polymor-phisms with type 2 diabetes. Diabetes 53:3007–3012.

8. Harley EA, Levens N (2003) Protein tyrosine phosphatase 1B inhibitors for the treat-ment of type 2 diabetes and obesity: Recent advances. Curr Opin Investig Drugs4:1179–1189.

9. Bourdeau A, Dube N, Tremblay ML (2005) Cytoplasmic protein tyrosine phosphatases,regulation and function: The roles of PTP1B and TC-PTP. Curr Opin Cell Biol 17:203–209.

10. Myers MP, et al. (2001) TYK2 and JAK2 are substrates of protein-tyrosine phosphatase1B. J Biol Chem 276:47771–47774.

11. Simoncic PD, et al. (2002) The T cell protein tyrosine phosphatase is a negative regulatorof janus family kinases 1 and 3. Curr Biol 12:446–453.

12. Renauld JC (2003) Class II cytokine receptors and their ligands: Key antiviral andinflammatory modulators. Nat Rev Immunol 3:667–676.

13. ten Hoeve J, et al. (2002) Identification of a nuclear Stat1 protein tyrosine phosphatase.Mol Cell Biol 22:5662–5668.

14. Heinonen KM, et al. (2004) T-cell protein tyrosine phosphatase deletion results inprogressive systemic inflammatory disease. Blood 103:3457–3464.

15. You-Ten KE, et al. (1997) Impaired bone marrow microenvironment and immunefunction in T cell protein tyrosine phosphatase–deficient mice. J Exp Med 186:683–693.

16. Bourdeau A, et al. (2007) TC-PTP–deficient bone marrow stromal cells fail to supportnormal B lymphopoiesis due to abnormal secretion of interferon-gamma. Blood109:4220–4228.

17. Kim HS, Lee MS (2007) STAT1 as a key modulator of cell death. Cell Signal 19:454–465.18. Yoshimura A (2006) Signal transduction of inflammatory cytokines and tumor devel-

opment. Cancer Sci 97:439–447.19. Simoncic PD, et al. (2006) T-cell protein tyrosine phosphatase (Tcptp) is a negative

regulator of colony-stimulating factor 1 signaling and macrophage differentiation.Mol Cell Biol 26:4149–4160.

20. Heinonen KM, et al. (2006) Protein tyrosine phosphatase 1B negatively regulatesmacrophage development through CSF-1 signaling. Proc Natl Acad Sci USA 103:2776–2781.

21. Dube N, et al. (2005) Genetic ablation of protein tyrosine phosphatase 1B accelerateslymphomagenesis of p53-null mice through the regulation of B-cell development.Cancer Res 65:10088–10095.

22. Porritt HE, et al. (2004) Heterogeneity among DN1 prothymocytes reveals multipleprogenitors with different capacities to generate T cell and non-T cell lineages.Immunity 20:735–745.

23. Schmidt-Arras DE, et al. (2005) Tyrosine phosphorylation regulates maturation ofreceptor tyrosine kinases. Mol Cell Biol 25:3690–3703.

24. Durbin JE, Hackenmiller R, Simon MC, Levy DE (1996) Targeted disruption of the mouseStat1 gene results in compromised innate immunity to viral disease. Cell 84:443–450.

25. Meraz MA, et al. (1996) Targeted disruption of the Stat1 gene in mice reveals unex-pected physiologic specificity in the JAK-STAT signaling pathway. Cell 84:431–442.

26. Alexander WS, et al. (1999) SOCS1 is a critical inhibitor of interferon gamma signalingand prevents the potentially fatal neonatal actions of this cytokine. Cell 98:597–608.

27. Liu B, et al. (2004) PIAS1 selectively inhibits interferon-inducible genes and is importantin innate immunity. Nat Immunol 5:891–898.

28. Starr R, et al. (1998) Liver degeneration and lymphoid deficiencies in mice lackingsuppressor of cytokine signaling-1. Proc Natl Acad Sci USA 95:14395–14399.

29. Gu D, et al. (1995) Myasthenia gravis–like syndrome induced by expression of inter-feron gamma in the neuromuscular junction. J Exp Med 181:547–557.

30. Seery JP, Carroll JM, Cattell V, Watt FM (1997) Antinuclear autoantibodies and lupusnephritis in transgenic mice expressing interferon gamma in the epidermis. J Exp Med186:1451–1459.

31. Sarvetnick N, et al. (1990) Loss of pancreatic islet tolerance induced by beta-cellexpression of interferon-gamma. Nature 346:844–847.

32. Toyonaga T, et al. (1994) Chronic active hepatitis in transgenic mice expressing inter-feron-gamma in the liver. Proc Natl Acad Sci USA 91:614–618.

33. Mullarky IK, et al. (2007) Gamma interferon suppresses erythropoiesis via interleukin-15. Infect Immun 75:2630–2633.

34. Thawani N, Tam M, Chang KH, Stevenson MM (2006) Interferon-gamma mediatessuppression of erythropoiesis but not reduced red cell survival following CpG-ODNadministration in vivo. Exp Hematol 34:1451–1461.

35. Borden EC, et al. (2007) Interferons at age 50: Past, current and future impact onbiomedicine. Nat Rev Drug Discov 6:975–990.

36. Shimizu T, et al. (2004) A novel mechanism for imatinib mesylate (STI571) resistance inCML cell line KT-1: Role of TC-PTP in modulating signals downstream from the BCR-ABLfusion protein. Exp Hematol 32:1057–1063.

37. Shimizu T, et al. (2003) STI571-resistant KT-1 cells are sensitive to interferon-alphaaccompanied by the loss of T-cell protein tyrosine phosphatase and prolonged phos-phorylation of Stat1. Exp Hematol 31:601–608.

38. Yu JM, et al. (1999) Expression of interferon-gamma by stromal cells inhibits murinelong-term repopulating hematopoietic stem cell activity. Exp Hematol 27:895–903.

39. Julien SG, et al. (2007) Protein tyrosine phosphatase 1B deficiency or inhibition delaysErbB2-induced mammary tumorigenesis and protects from lung metastasis. Nat Genet39:338–346.

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