The Fujise Lab

Overview

In 1999, Dr. Fujise, while performing yeast-two hybrid screening, identified a then-poorly-characterized molecule that specifically interacted with myeloid cell leukemia-1 protein (MCL1), a macrophage survival factor. The molecule was fortilin [1]. The Lab has characterized fortilin since then at both molecular and translational levels.  A review on the role of fortilin in human diseases is available [2].

Fortilin—A Multifunctional Molecule

Fortilin (also known as translationally controlled tumor protein, histamine-releasing factor) is a ubiquitously expressed and highly conserved 172-amino acid, 20-kDa protein. Fortilin is present in intracellular [1] and extracellular spaces [3]. Intracellularly, fortilin has been detected in both the nucleus and the cytosol [1]. Although it was originally cloned in 1988 by Gross et al. as a molecule abundantly expressed in tumor cells [4], the function of fortilin remained unknown until 2001 when we and others reported that fortilin blocks apoptosis [1, 5, 6].

The mechanism by which fortilin does so is multifactorial; it positively regulates anti-apoptotic molecules such as PRX1 [7] and MCL1 [8, 9] and negatively regulates pro-apoptotic molecules such as IRE1α [10] and p53 [11, 12]. More recently, fortilin has been recognized as a multi-functional protein with roles in various cellular processes, including cell cycle progression [13] and IgE-mediated histamine release and allergic reactions [14, 15].

Intracellular fortilin

In the cell, fortilin exerts its biological activities through molecular interactions with “executioner” proteins. In the cytosol, fortilin binds to and positively regulates PRX1, an enzyme that detoxifies a reactive oxygen species (ROS). More specifically, fortilin protects PRX1 from proteasome-mediated degradation and prevents it from being inactivated by the Mst1 kinase [7]. In addition, fortilin binds to MCIL1, an anti-apoptotic Bcl-2 family member, and protects it from proteasome-mediated degradation, supporting the survival of myeloid cells [8, 9]. Moreover, fortilin interacts with and inhibits the activity of IRE1α, an endoplasmic reticulum stress sensor [10]. In the nucleus, fortilin binds to p53 and prevents it from transcriptionally activating BAX, PUMA, and NOXA [11, 12]. Fortilin has also been shown to bind to several nuclear proteins, including histone H4 and the transcription factor BTF3 [16], although the biological significance of such interactions is unknown.

Extracellular fortilin

We and others have shown that fortilin is secreted from the cell [3] via the non-classical pathway [17] and circulates in the blood of humans and mice [3]. However, the biological role of circulating fortilin remained unknown. We recently reported that extracellular fortilin binds TGF-β1 and prevents TGF-β receptor activation [Communications Biology 2022:5:157].

Fortilin Promotes Atherosclerosis

Because MCL1 is a macrophage (MΦ) survival factor and MΦ play a key facilitative role in the pathogenesis of atherosclerosis, we hypothesized that fortilin facilitates atherosclerosis. Our group was the first to definitively show this to be true. Immunohistochemical analyses of human and mouse atherosclerotic tissue showed abundant fortilin immunogenicity in the area of atherosclerosis. We first generated fortilin-deficient (fortilin+/-) and wild-type mice (fortilin+/+) on a LDL receptor and apolipoprotein B mRNA editing enzyme catalytic polypeptide 1 double knockout (Ldlr-/-Apobec1-/-) hypercholesgterolemic genetic background, incubated them for 10 months on a normal chow diet to recapitulate human atherosclerosis as much as logistically possible, and assessed the degree and extent of atherosclerosis. Strikingly, fortilin+/- mice exhibited significantly less atherosclerosis in their aortae than their fortilin+/+ litter mate controls with identical blood pressure and lipid profile for both groups [18]. 

Fortilin Protects the Liver Against Alcohol-Induced Damage

Because fortilin augments the peroxidase activity of PRX1 in vitro, we tested whether overexpression of fortilin in the liver protects the liver against alcohol-induced, oxidative-stress-mediated injury, using the mouse strain that overexpresses fortilin specifically in hepatocytes. We found that the liver-specific overexpression of fortilin reduced PRX1 phosphorylation in the liver, enhanced PRX1 activity, and protected the transgenic animals against alcohol-induced, ROS-mediated, liver damage as evidenced by the decreased serum alanine aminotransferase (ALT) levels and decreased malondialdehyde (MDA) and 4-hydroxy-2-nonenal (4-HNE) levels in the liver [7].

References

  1. Li, F., Zhang, D. and Fujise, K. Characterization of Fortilin, a Novel Anti-Apoptotic Protein. J Biol Chem 2001;276:47542-47549.
  1. Pinkaew, D. and Fujise, K. Fortilin: A Potential Target for the Prevention and Treatment of Human Diseases. Adv Clin Chem 2017;82:265-300.
  1. Sinthujaroen, P., Wanachottrakul, N., Pinkaew, D., Petersen, J., Phongdara, A., Sheffield-Moore, M. and Fujise, K. Elevation of Serum Fortilin Levels Is Specific for Apoptosis and Signifies Cell Death in Vivo. BBA Clinical 2014;2:103-111.
  1. Gross, B., Gaestel, M., Bohm, H. and Bielka, H. Cdna Sequence Coding for a Translationally Controlled Human Tumor Protein. Nucleic Acids Res 1989;17:8367.
  1. Tuynder, M., Susini, L., Prieur, S., Besse, S., Fiucci, G., Amson, R. and Telerman, A. Biological Models and Genes of Tumor Reversion: Cellular Reprogramming through Tpt1/Tctp and Siah-1. Proc Natl Acad Sci U S A 2002;99:14976-81.
  1. Yang, Y., Yang, F., Xiong, Z., Yan, Y., Wang, X., Nishino, M., Mirkovic, D., Nguyen, J., Wang, H. and Yang, X.F. An N-Terminal Region of Translationally Controlled Tumor Protein Is Required for Its Antiapoptotic Activity. Oncogene 2005;24:4778-88.
  1. Chattopadhyay, A., Pinkaew, D., Doan, H.Q., Jacob, R.B., Verma, S.K., Friedman, H., Peterson, A.C., Kuyumcu-Martinez, M.N., Mcdougal, O.M. and Fujise, K. Fortilin Potentiates the Peroxidase Activity of Peroxiredoxin-1 and Protects against Alcohol-Induced Liver Damage in Mice. Sci Rep 2016;6:18701.
  1. Graidist, P., Phongdara, A. and Fujise, K. Antiapoptotic Protein Partners Fortilin and Mcl1 Independently Protect Cells from 5-Fu-Induced Cytotoxicity. J Biol Chem 2004;279:40868-75.
  1. Zhang, D., Li, F., Weidner, D., Mnjoyan, Z.H. and Fujise, K. Physical and Functional Interaction between Mcl1 and Fortilin. The Potential Role of Mcl1 as a Fortilin Chaperone. J Biol Chem 2002;277:37430-37438.
  1. Pinkaew, D., Chattopadhyay, A., King, M.D., Chunhacha, P., Liu, Z., Stevenson, H.L., Chen, Y., Sinthujaroen, P., Mcdougal, O.M. and Fujise, K. Fortilin Binds Ire1α and Prevents Er Stress from Signaling Apoptotic Cell Death. Nat Commun 2017;8:1-16.
  1. Chen, Y., Fujita, T., Zhang, D., Doan, H., Pinkaew, D., Liu, Z., Wu, J., Koide, Y., Chiu, A., Lin, C.C., Chang, J.Y., Ruan, K.H. and Fujise, K. Physical and Functional Antagonism between Tumor Suppressor Protein P53 and Fortilin, an Anti-Apoptotic Protein. J Biol Chem 2011;286:32575-85.
  1. Amson, R., Pece, S., Lespagnol, A., Vyas, R., Mazzarol, G., Tosoni, D., Colaluca, I., Viale, G., Rodrigues-Ferreira, S., Wynendaele, J., Chaloin, O., Hoebeke, J., Marine, J.C., Di Fiore, P.P. and Telerman, A. Reciprocal Repression between P53 and Tctp. Nat Med 2011;18:91-99.
  1. Yarm, F.R. Plk Phosphorylation Regulates the Microtubule-Stabilizing Protein Tctp. Mol Cell Biol 2002;22:6209-21.
  1. Kashiwakura, J.I., Ando, T., Matsumoto, K., Kimura, M., Kitaura, J., Matho, M.H., Zajonc, D.M., Ozeki, T., Ra, C., Macdonald, S.M., Siraganian, R.P., Broide, D.H., Kawakami, Y. and Kawakami, T. Histamine-Releasing Factor Has a Proinflammatory Role in Mouse Models of Asthma and Allergy. J Clin Invest 2011;122:218-228.
  1. Macdonald, S.M., Rafnar, T., Langdon, J. and Lichtenstein, L.M. Molecular Identification of an Ige-Dependent Histamine-Releasing Factor. Science 1995;269:688-90.
  1. Kobayashi, D., Tokuda, T., Sato, K., Okanishi, H., Nagayama, M., Hirayama, M., Ohtsuki, S. and Araki, N. Identification of a Specific Translational Machinery Via Tctp-Ef1a2 Interaction Regulating Nf1-Associated Tumor Growth by Affinity Purification and Data-Independent Mass Spectrometry Acquisition (Ap-Dia/Swath). Mol Cell Proteomics 2018.
  1. Amzallag, N., Passer, B.J., Allanic, D., Segura, E., Thery, C., Goud, B., Amson, R. and Telerman, A. Tsap6 Facilitates the Secretion of Translationally Controlled Tumor Protein/Histamine-Releasing Factor Via a Nonclassical Pathway. J Biol Chem 2004;279:46104-12.
  1. Pinkaew, D., Le, R.J., Chen, Y., Eltorky, M., Teng, B.B. and Fujise, K. Fortilin Reduces Apoptosis in Macrophages and Promotes Atherosclerosis. Am J Physiol Heart Circ Physiol 2013;305:H1519-29.