Proteolytic processing of TGFalpha redirects its mitogenic activity: the membrane-anchored form is autocrine, the secreted form is paracrine

Wild-type transforming growth factor alpha (TGFalpha) expression in lactotrope cells in the pituitary gland led to lactotrope-specific pituitary hyperplasia and adenomata. To indicate whether the EGF receptor is involved in this TGFalpha-mediated phenotype, we bred TGFalpha mice with mice expressing the cytoplasmic truncated-EGF receptor (EGFR-tr), which is dominant-negative in other models. These bitransgenic mice developed pituitary pathology despite expression of the dominant-negative receptor. To further characterize this observation, we generated two lineages of transgenic mice that overexpress mutant forms of TGFalpha: a processed soluble form (s TGFalpha) and a cytoplasmic-deleted form (TGFalphaDeltaC). While sTGFalpha expression in lactotrope cells failed to induce autocrine lactotrope hyperplasia, the pituitary became very enlarged due to proliferation of neighboring interstitial cells. In contrast, the TGFalphaDeltaC mice did not develop a phenotype, although the mRNA and protein were present in the pituitary and this form of TGFalpha was confirmed to be biologically active and targeted properly to the plasma membrane of cultured CHO cells. The results suggest that the cytoplasmic domain of TGFalpha is required for autocrine parenchymal tumor formation in the pituitary gland. This signal cannot be inhibited by the EGFR-tr. Conversely, the released form of TGFalpha appears to have primarily paracrine activity.     

Transforming growth factor-alpha short-circuits downregulation of the epidermal growth factor receptor

Transforming growth factor-alpha (TGFalpha) is an epidermal growth factor receptor (EGFR) ligand which is distinguished from EGF by its acid-labile structure and potent transforming function. We recently reported that TGFalpha induces less efficient EGFR heterodimerization and downregulation than does EGF (Gulliford et al., 1997, Oncogene, 15:2219-2223). Here we use isoform-specific EGFR and ErbB2 antibodies to show that the duration of EGFR signalling induced by a single TGFalpha exposure is less than that induced by equimolar EGF. The protein trafficking inhibitor brefeldin A (BFA) reduces the duration of EGF signalling to an extent similar to that seen with TGFalpha alone; the effects of TGFalpha and BFA on EGFR degradation are opposite, however, with TGFalpha sparing EGFR from downregulation but BFA accelerating EGF-dependent receptor loss. This suggests that BFA blocks EGFR recycling and thus shortens EGF-dependent receptor signalling, whereas TGFalpha shortens receptor signalling and thus blocks EGFR downregulation. Consistent with this, repeated application of TGFalpha is accompanied by prolonged EGFR expression and signalling, whereas similar application of EGF causes receptor downregulation and signal termination. These findings indicate that constitutive secretion of pH-labile TGFalpha may perpetuate EGFR signalling by permitting early oligomer dissociation and dephosphorylation within acidic endosomes, thereby extinguishing a phosphotyrosine-based downregulation signal and creating an irreversible autocrine growth loop.     

Teratogenic effects of retinoic acid are modulated in mice lacking expression of epidermal growth factor and transforming growth factor-alpha

BACKGROUND: Epidermal growth factor (EGF) and transforming growth factor-alpha (TGFalpha) regulate cell proliferation and differentiation in the embryo. The induction of cleft palate (CP) by all trans-retinoic acid (RA) was associated with altered expression of TGFalpha, EGF receptor, and binding of EGF. This study uses knockout (KO) mice to examine the roles of EGF and TGFalpha in teratogenic responses of embryos exposed to RA. METHODS: Pregnant wild-type (WT) mice of mixed genetic background, EGF KO, C57BL/6J, and TGFalpha KO mice were given a single oral dose of RA (100 mg/kg, 10 ml/kg) or corn oil on GD 10 at 12 PM, GD 11 at 12 PM or 4 PM, or GD 12 at 8 AM or 12 PM (plug day = GD 0). GD 18 fetuses were examined for external, visceral, and skeletal effects. RESULTS: After exposure to RA on GD 12, the incidence of CP in EGF KO was significantly reduced relative to WT. In TGFalpha KO fetuses, RA exposure on GD 10 increased the incidence of CP versus C57BL/6J. The incidence of skeletal defects in the limbs, vertebrae, sternebrae, and ribs were also affected by lack of expression of EGF or TGFalpha with region-specific amelioration or exacerbation of the effects of RA. In TGFalpha KO fetuses, incidences of forelimb long bone and digit defects increased relative to C57BL/6J. In EGF KO fetuses, relative to WT, the incidence of hindlimb oligodactyly was increased. In EGF KO, but not WT, RA produced short, bent radius, humerus, and ulna. Both TGFalpha and EGF KO mice had increased incidences of dilation of the renal pelvis and this was reduced by RA. CONCLUSIONS: RA exposure produced skeletal and visceral defects in all genotypes; however, EGF or TGFalpha KO influenced the incidence and severity of defects. This study supports a role for EGF and TGFalpha in the response to RA.     

A diphtheria toxin receptor deficient in epidermal growth factor-like biological activity

Targeted cell ablation in animals is a powerful method for analyzing the physiological function of cell populations and generating various animal models of organ dysfunction. To achieve more specific and conditional ablation of target cells, we have developed a method termed Toxin Receptor mediated Cell Knockout (TRECK). A potential shortcoming of this method, however, is that overexpression of human heparin-binding epidermal growth factor-like growth factor (hHB-EGF) as a diphtheria toxin (DT) receptor in target cells or tissues may cause abnormalities in transgenic mice, since hHB-EGF is a member of the EGF growth factor family. To create novel DT receptors that are defective in growth factor activity and resistant to metalloprotease-cleavage, we mutated five amino acids in the extracellular EGF-like domain of hHB-EGF, which contains both DT-binding and protease-cleavage sites. Two of the resultant hHB-EGF mutants, I117A/L148V and I117V/L148V, possessed little growth factor activity but retained DT receptor activity. Furthermore, these mutants were resistant to metalloprotease-cleavage by 12-O-tetradecanoylphorbol-13-acetate stimulation, which is expected to enhance DT receptor activity. These novel DT receptors should be useful for the generation of transgenic mice by TRECK.     

Effects of epidermal growth factor (EGF), transforming growth factor-alpha (TGFalpha), and 2,3,7,8-tetrachlorodibenzo-p-dioxin on fusion of embryonic palates in serum-free organ culture using wild-type, EGF knockout, and TGFalpha knockout mouse strains

BACKGROUND: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is teratogenic in mice, producing cleft palate (CP). TCDD exposure disrupts expression of epidermal growth factor (EGF) receptor, EGF, and transforming growth factor-alpha (TGFalpha) in the palate and affects proliferation and differentiation of medial epithelial cells. EGF knockout embryos are less susceptible to the induction of CP by TCDD. This study used palate organ culture to examine the hypothesis that EGF enables a response to TCDD. METHODS: The midfacial tissues from wild-type (WT), EGF knockout, C57BL/6J, and TGFalpha knockout embryos were placed in organ culture on gestational day (GD) 12. Palatal explants were cultured for 4 days in serum-free Bigger's (BGJ) medium with 0.1% dimethyl sulfoxide (DMSO) or 1 x 10(-8) M TCDD with or without 2 ng of EGF/ml, 1 or 2 ng of TGFalpha/ml. Effects on palatal fusion were evaluated on day 4 of culture. EGF levels in explants and medium were determined using Luminex technology. RESULTS: In serum-free, control medium, palates from all of the strains fused. EGF knockout palates cultured with TCDD (no EGF) fused, but those cultured with TCDD + 2 ng of EGF/ml failed to fuse (p < 0.05 vs. control or TCDD without EGF). TGFalpha knockout palates failed to fuse when cultured with TCDD + 2 ng of TGFalpha/ml. EGF levels increased in tissue and accumulated in the medium after 24 hr of culture. CONCLUSIONS: This study demonstrated that providing EGF to the palates of EGF knockout mice restored the response to TCDD. These studies support the hypothesis that the mechanism for induction of CP by TCDD is mediated via the EGFR pathway.     

Tissue localization of TGFα and apoptosis are inversely related in colorectal tumors

Expression of TGFalpha and the EGF receptor was studied in relation to apoptosis in human colorectal mucosa and premalignant and malignant tumors. In normal mucosa the proteins colocalized both in the proliferation compartment and at the luminal pole of the crypts in cells committed to undergo apoptosis. While staining for the EGF receptor was increased in premalignant and malignant lesions, TGFalpha was undetectable in aberrant crypt foci as well as large areas of adenomas. Incidence of apoptosis (AI) was high in these areas ranging from 8.83-24.59. Adenomas did, however, contain islands of high TGFalpha expression where AI was decreased to a range of 0.76-4.00 (decreased at P=0.0027). In carcinomas TGFalpha expression was increased above both normal and adenoma levels corresponding to the decrease in apoptosis in the malignant tumors. Tissue localization of TGFalpha and AI were still inversely related ( P=0.022), but interpatient variability was much larger than for adenomas. The data indicate that TGFalpha is the main survival factor in premalignant tumor cells of the colon, while additional factors moderate its effect in carcinomas. This suggests the possibility of targeting the EGF receptor pathway not only for treatment but also for the reversal of adenoma growth and the prevention of malignant colorectal tumors.     

Localization of the epidermal growth factor (EGF) in the epididymis and accessory genital glands of the boar and functional effects on spermatozoa

The epidermal growth factor (EGF) family plays an important role in reproductive function regulation. The aim of this work was to investigate the localization of EGF, transforming growth factor alpha (TGFalpha) and epidermal growth factor receptor (EGFr) in boar epididymis and accessory genital glands, as well as study the presence of EGFr and the effects of EGF on boar spermatozoa. In the epididymis, prostate and vesicular glands EGF, TGFalpha and EGFr were detected in the pseudostratified epithelium. None of them were observed in the bulbourethral glands. Epidermal growth factor receptor was detected by immunofluorescence in non-capacitated, capacitated and acrosome reacted spermatozoa. Confocal microscopy revealed different staining patterns over the head, midpiece and/or flagellum whereas, flow cytometry analysis showed that the population of positive spermatozoa did not exceed 58% and did not depend on the functional state. To study the effects of EGF, spermatozoa were capacitated in Tyrodes medium containing 0, 10 and 100ng/ml EGF. Acrosome status, membrane integrity and motility patterns were evaluated after capacitation and after the acrosome reaction (AR). Capacitation in the presence of 100ng/ml EGF significantly improved the quality of movement (P<0.01) after the AR. These findings suggest that EGF and TGFalpha are produced in the reproductive tract of the boar where they may act locally and/or on a population of spermatozoa, improving the quality of movement after the AR.     

Cross-talk between epidermal growth factor receptor and c-Met signal pathways in transformed cells

In rat liver epithelial cells constitutively expressing transforming growth factor alpha (TGFalpha), c-Met is constitutively phosphorylated in the absence of its ligand, hepatocyte growth factor. We proposed that TGFalpha and the autocrine activation of its receptor, epidermal growth factor receptor (EGFR), leads to phosphorylation and activation of c-Met. We found that there is constitutive c-Met phosphorylation in human hepatoma cell lines and the human epidermoid carcinoma cell line, A431 which express TGFalpha, but not in normal human hepatocytes. Constitutive c-Met phosphorylation in A431, HepG2, AKN-1, and HuH6 cells was inhibited by neutralizing antibodies against TGFalpha and/or EGFR. Exposure to exogenous TGFalpha or EGF increased the phosphorylation of c-Met in the human epidermoid carcinoma cell line, A431. The increase of c-Met phosphorylation by TGFalpha in A431 cells was inhibited by neutralizing antibodies against TGFalpha and/or EGFR and by the EGFR-specific inhibitor tyrphostin AG1478. These results indicate that constitutive c-Met phosphorylation, and the increase of c-Met phosphorylation by TGFalpha or EGF, in tumor cell lines is the result of the activation via EGFR. We found that c-Met in tumor cells co-immunoprecipitates with EGFR regardless of the existence of their ligands in tumor cells, but not in normal human hepatocytes. We conclude that c-Met associates with EGFR in tumor cells, and this association facilitates the phosphorylation of c-Met in the absence of hepatocyte growth factor. This cross-talk between c-Met and EGFR may have significant implications for altered growth control in tumorigenesis.     

Role of epidermal growth factor and its receptor in chemotherapy-induced intestinal injury

Several growth factors are trophic for the gastrointestinal tract and able to reduce the degree of intestinal damage caused by cytotoxic agents. However, studies of epidermal growth factor (EGF) for chemotherapy-induced intestinal injury are conflicting. The development of a transgenic mouse that specifically overexpresses EGF in the small intestine provided a unique opportunity to assess the contribution of EGF in mucositis. After a course of fluorouracil, transgenic mice fared no better than control mice. Weight recovery was inferior, and mucosal architecture was not preserved. Apoptosis was not decreased and proliferation was not increased in the crypts. To corroborate the findings in transgenic mice, ICR mice were treated with exogenous EGF after receiving fluorouracil. Despite ileal upregulation of native and activated EGF receptor, the mice were not protected from intestinal damage. No benefits were observed with different EGF doses or schedules or routes of EGF administration. Finally, mucositis was induced in mutant mice with specific defects of the EGF signaling axis. Compared with control mice, clinical and histological parameters of intestinal injury after fluorouracil were no different in waved-2 mice, which have functionally diminished EGF receptors, or waved-1 mice, which lack transforming growth factor-alpha, another major ligand for the EGF receptor. These findings do not support a critical role for EGF or its receptor in chemotherapy-induced intestinal injury.     

Expression of a dominant negative mutant of epidermal growth factor receptor in the epidermis of transgenic mice elicits striking alterations in hair follicle development and skin structure.

Epidermal growth factor receptor (EGFR) is a key regulator of keratinocyte biology. However, the physiological role of EGFR in vivo has not been well established. To analyze the role of EGFR in skin, we have generated transgenic mice expressing an EGFR dominant negative mutant in the basal layer of epidermis and outer root sheath of hair follicles. Mice expressing the mutant receptor display short and waved pelage hair and curly whiskers during the first weeks of age, but subsequently pelage and vibrissa hairs become progressively sparser and atrophic. Eventually, most mice present severe alopecia. Histological examination of the skin of transgenic mice shows striking alterations in the development of hair follicles, which fail to enter into catagen stage. These alterations eventually lead to necrosis and disappearance of the follicles, accompanied by strong infiltration of the skin with inflammatory elements. The interfollicular epidermis of these mice shows marked hyperplasia, expression of hyperproliferation-associated keratin K6 and increased 5-bromo-2-deoxyuridine incorporation. EGFR function was inhibited in transgenic skin keratinocytes, since in vivo and in vitro autophosphorylation of EGFR was almost completely abolished on EGF stimulation. These results implicate EGFR in the control of hair cycle progression, and provide new information about its role in epidermal growth and differentiation.     

Transforming growth factor alpha protects against Fas-mediated liver apoptosis in mice

The Fas/Fas ligand interaction plays a crucial role in various liver diseases, and administration of agonistic anti-Fas antibody to mice causes massive hepatic apoptosis and fulminant hepatic failure. Several growth factors have recently been found to function in preventing apoptosis. In this study, we demonstrated that overexpression of transforming growth factor alpha (TGFalpha) has a dramatic protective effect on Fas-mediated hepatic apoptosis at the biochemical and histological levels. Moreover, 85.7% (six out of seven) of TGFalpha transgenic mice survived the lethal liver damage, whereas all wild-type mice died. Expression of Bcl-xL, an anti-apoptotic protein, was greatly increased in the transgenic mice. Taken together, our findings suggest that TGFalpha protects against Fas-mediated liver apoptosis in vivo and up-regulation of Bcl-xL may participate in protective effect of TGFalpha.     

Expression of epidermal growth factor in transgenic mice causes growth retardation

The epidermal growth factor (EGF) family of peptides signals through the erbB family of receptor tyrosine kinases and plays important roles in development and tumorigenesis. Both EGF and transforming growth factor (TGF)-alpha only bind to erbB1 and activate it. The precursor of EGF is distinct from that of TGF-alpha in having eight additional EGF-like repeats. We have recently shown that the EGF precursor without these repeats is biologically active and leads to hypospermatogenesis in transgenic mice. Here we present evidence that the growth of transgenic mice widely expressing this engineered EGF precursor is also stunted. These mice were consistently born at half the normal weight and reached almost 80% of normal weight at adulthood. The mechanism involved a reduction of serum insulin-like growth factor-binding protein-3. Chondrocyte development in the growth plate was affected, and osteoblasts accumulated in the endosteum and periosteum. Besides these novel findings on the in vivo effects of EGF on bone development, we observed no sign of tumor formation in our transgenic animals. In contrast to previous reports on TGF-alpha transgenic mice, we show that the biological functions of EGF and TGF-alpha are clearly distinct.     

Autocrine activation of EGF receptor promotes oscillation of glutamate-induced calcium increase in astrocytes cultured in rat cerebral cortex

We previously reported that astrocytes cultured for more than 2 days in a defined medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) showed calcium oscillation in response to glutamate, whereas the response pattern was transient in the absence of the exogenous growth factors. In the present study, we found that astrocytes showed glutamate-induced calcium oscillation, even in growth factor-free medium, if the cells had been cultured for more than 5 days. The calcium oscillation promoted by the prolonged culture period was suppressed by an inhibitor of EGF receptor tyrosine kinase, but not by a neutralizing antibody to bFGF, indicating that the accumulation of an autocrine factor that activates the EGF receptor leads to calcium oscillation. Astrocytes in our culture system expressed EGF, transforming growth factor alpha (TGFalpha), bFGF and acidic fibroblast growth factor (aFGF). Exogenous aFGF, which induced astrocyte immediate early gene expression to the same extent as EGF or bFGF, did not affect calcium oscillation. Exogenous EGF and bFGF promoted astrocyte hypertrophic morphology and proliferation, as well as calcium oscillation. In contrast, these properties did not accompany calcium oscillation induced by the prolonged culture period. These results suggest that astrocytes possess the ability to promote their own calcium oscillation, which is independent of hypertrophic changes to reactive astrocytes.     

HB-EGF promotes epithelial cell migration in eyelid development

Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of growth factors that binds to and activates the EGF receptor (EGFR) and ERBB4. Here, we show that HB-EGF-EGFR signaling is involved in eyelid development. HB-EGF expression is restricted to the tip of the leading edge of the migrating epithelium during eyelid closure in late gestation mouse embryos. Both HB-EGF null (HB(del/del)) and secretion-deficient (HB(uc/uc)) mutant embryos exhibited delayed eyelid closure, owing to slower leading edge extension and reduced actin bundle formation in migrating epithelial cells. No changes in cell proliferation were observed in these embryos. In addition, activation of EGFR and ERK was decreased in HB(del/del) eyelids. Crosses between HB(del/del) mice and waved 2 mice, a hypomorphic EGFR mutant strain, indicate that HB-EGF and EGFR interact genetically in eyelid closure. Together with our data showing that embryos treated with an EGFR-specific kinase inhibitor phenocopy HB(del/del) embryos, these data indicate that EGFR mediates HB-EGF-dependent eyelid closure. Finally, analysis of eyelid closure in TGFalpha-null mice and in HB-EGF and TGFalpha double null mice revealed that HB-EGF and TGFalpha contribute equally to and function synergistically in this process. These results indicate that soluble HB-EGF secreted from the tip of the leading edge activates the EGFR and ERK pathway, and that synergy with TGFalpha is required for leading edge extension in epithelial sheet migration during eyelid closure.     

The use of c-src knockout mice for the identification of the main toxic signaling pathway of TCDD to induce wasting syndrome

The effect of single intraperitoneal injection of 115 microg/kg of TCDD (i.e., approximately 1/2 of LD50) to male C57BL/6 mice on the liver mRNA expression changes of several growth factor related genes was assessed at 3 h, 24 h, 10 days, and 30 days posttreatment. The results revealed that the most consistently elevated mRNAs during the entire test period were those of c-Src, TGFalpha, and PDGFa. In contrast, those observed to be consistently suppressed were mRNAs for EGF receptor (EGFR), Ki-Ras, SAPKK, Sp-1, C/EBPbeta, and NFkB. Elevation of mRNAs for TGFbeta and STAT3 was observed only on day 10 and day 30. To assess the role of c-Src in the above action of TCDD, we conducted a parallel study with congenic C57BL/6 male c-src -/- mice. The results showed that in scr -/- mice the effect of TCDD was less in the case of mRNA expression of PDGF(AA), STAT3, C/EPBbeta, NMT-1, and AP-2gamma in addition to c-src as compared to scr +/+ mice. Those affected least by the absence of c-Src were SAPKK, and surprisingly, EGF receptor mRNAs, both of which were consistently downregulated in both strains. In most of the other cases, the extent of TCDD-induced changes were generally less pronounced in src -/- mice as compared to +/+ mice. These observations support the notion that c-Src is an important mediator of the effects of TCDD on TGFalpha, PDGF(AA), and C/EBPalpha, beta.     

Development of mouse embryos after immunoneutralization of mitogenic growth factors mimics that of cloned embryos

The extent to which mitogenic growth factors influence embryo development is not well characterized. We sought to determine the effect of epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) on naturally fertilized (in vivo-derived) and in vitro-fertilized mouse embryos, compared with that on cloned (intracytoplasmic nuclear injection-derived) mouse embryos, in which EGF and TGFalpha expression is markedly reduced. Immunoneutralization of EGF, TGFalpha, and EGF receptor by using specific antibodies significantly reduced the blastocyst development rate (in vivo-derived: 66%, 63%, and 63%, respectively; in vitro-fertilized: 57%, 55%, and 56%, respectively), increased the number of apoptotic nuclei (in vivo-derived: 9%, 10%, and 9%, respectively; in vitro-fertilized: 13%, 13%, and 13%, respectively), decreased the total number of cells (in vivo-derived: 87%, 85%, and 86%, respectively; in vitro-fertilized: 86%, 85%, and 86%, respectively), and increased the inner cell mass:trophectoderm ratios (in vivo-derived: 1:2.70 +/- 0.05, 1:2.73 +/- 0.04, 1:2.71 +/- 0.06, respectively; in vitro-fertilized: 1:2.94 +/- 0.02, 1:2.96 +/- 0.02, 1:2.95 +/- 0.02, respectively). In most cases, combined treatment with neutralizing antibodies to both EGF and TGFalpha accentuated changes in these parameters. Further, the effect of combined immunoneutralization on these parameters in fertilized embryos was no different from those in cloned embryos. Therefore, normal expression of mitogenic growth factors is crucial for successful development of mouse embryos before implantation. Inhibiting the action of mitogenic growth factors causes fertilized embryos to exhibit developmental characteristics similar to those of cloned embryos, which may partially explain the poor developmental potential of cloned mammalian embryos.     

Generation of an environmental niche for neural stem cell development by the extracellular matrix molecule tenascin C

Stem cells in the embryonic mammalian CNS are initially responsive to fibroblast growth factor 2 (FGF2). They then undergo a developmental programme in which they acquire epidermal growth factor (EGF) responsiveness, switch from the production of neuronal to glial precursors and become localized in specialized germinal zones such as the subventricular zone (SVZ). Here we show that extracellular matrix molecules act as regulators of this programme. Tenascin C is highly expressed in the SVZ, and transgenic mice lacking tenascin C show delayed acquisition of the EGF receptor. This results from alterations in the response of the stem cells to the growth factors FGF2 and bone morphogenic protein 4 (BMP4), which normally promote and inhibit acquisition of the EGF receptor, respectively. Tenascin C-deficient mice also have altered numbers of CNS stem cells and these stem cells have an increased probability of generating neurones when grown in cell culture. We conclude that tenascin C contributes to the generation of a stem cell 'niche' within the SVZ, acting to orchestrate growth factor signalling so as to accelerate neural stem cell development.     

The F-BAR Protein PACSIN2 Regulates Epidermal Growth Factor Receptor Internalization

Signaling via growth factor receptors, including the epidermal growth factor (EGF) receptor, is key to various cellular processes, such as proliferation, cell survival, and cell migration. In a variety of human diseases such as cancer, aberrant expression and activation of growth factor receptors can lead to disturbed signaling. Intracellular trafficking is crucial for proper signaling of growth factor receptors. As a result, the level of cell surface expression of growth factor receptors is an important determinant for the outcome of downstream signaling. BAR domain-containing proteins represent an important family of proteins that regulate membrane dynamics. In this study, we identify a novel role for the F-BAR protein PACSIN2 in the regulation of EGF receptor signaling. We show that internalized EGF as well as the (activated) EGF receptor translocated to PACSIN2-positive endosomes. Furthermore, loss of PACSIN2 increased plasma membrane expression of the EGF receptor in resting cells and increased EGF-induced phosphorylation of the EGF receptor. As a consequence, EGF-induced activation of Erk and Akt as well as cell proliferation were enhanced in PACSIN2-depleted cells. In conclusion, this study identifies a novel role for the F-BAR-domain protein PACSIN2 in regulating EGF receptor surface levels and EGF-induced downstream signaling.