Growth differentiation factor 15 (GDF15) is a divergent member of the TGFβ superfamily. It is also called macrophage inhibitory cytokine 1 (MIC1) (Bootcov M R, 1997, Proc Natl Acad Sci 94:11514-9), placental bone morphogenetic factor (PLAB) (Hromas R 1997, Biochim Biophys Acta. 1354:40-4), placental transforming growth factor beta (PTGFB) (Lawton L N 1997, Gene. 203:17-26), prostate derived factor (PDF) (Paralkar V M 1998, J Biol Chem. 273:13760-7), and nonsteroidal anti-inflammatory drug-activated gene (NAG-1) (Baek S J 2001, J Biol Chem. 276: 33384-92).
Human GDF15 gene is located on chromosome 19p13.2-13.1; rat GDF15 gene is located on chromosome 16; and mouse GDF15 gene is located on chromosome 8. The GDF15 open reading frames span two exons (Bottner M 1999, Gene. 237:105-11 and NCBI). The mature GDF15 peptide shares low homology with other family members (Katoh M 2006, Int J Mol Med. 17:951-5.).
GDF15 is synthesized as a large precursor protein that is cleaved at the dibasic cleavage site to release the carboxyterminal mature peptide. The mouse and rat GDF15 prepro-peptides both contain 303 amino acids. Human full-length precursor contains 308 amino acids. The rodent mature peptides contain 115 amino acids after processing at the RGRR (SEQ ID NO:1) cleavage site. The human mature peptide contains 112 amino acids after processing at the RGRRRAR (SEQ ID NO:2) cleavage site. Human mature GDF15 peptide shares 66.1% and 68.1% sequence similarity with rat and mouse mature GDF15 peptides (Bottner M 1999, Gene. 237:105-11; Bauskin A R 2000, EMBO J. 19:2212-20; NCBI). There is no glycosylation site in the mature GDF15 peptide.
The mature GDF15 peptide contains the seven conserved cysteine residues required for the formation of the cysteine knot motif (having three intrachain disulfide bonds) and the single interchain disulfide bond that are typical for TGFβ superfamily members. The mature GDF15 peptide further contains two additional cysteine residues that form a fourth intrachain disulfide bond. Biologically active GDF15 is a 25 KD homodimer of the mature peptide covalently linked by one interchain disulfide bond.
GDF15 circulating levels have been reported to be elevated in multiple pathological and physiological conditions, most notably pregnancy (Moore A G 2000. J Clin Endocrinol Metab 85: 4781-4788), β-thalassemia (Tanno T 2007, Nat Med 13:1096-101; Zimmermann M B, 2008 Am J Clin Nutr 88:1026-31), and congenital dyserythropoietic anemia (Tamary H 2008, Blood. 112:5241-4). GDF15 has also been linked to multiple biological activities in literature reports. Studies of GDF15 knockout and transgenic mice suggested that GDF15 may be protective against ischemic/reperfusion- or overload-induced heart injury (Kempf T, 2006, Circ Res. 98:351-60; Xu J, 2006, Circ Res. 98:342-50), protective against aging-associated motor neuron and sensory neuron loss (Strelau J, 2009, J Neurosci. 29:13640-8), mildly protective against metabolic acidosis in kidney, and may cause cachexia in cancer patients (Johnen H 2007 Nat Med. 11:1333-40). Many groups also have studied the role of GDF15 in cell apoptosis and proliferation and reported controversial results using different cell culture and xenograft models. Studies on transgenic mice showed that GDF15 is protective against carcinogen or Apc mutation induced neoplasia in intestine and lung (Baek S J 2006, Gastroenterology. 131:1553-60; Cekanova M 2009, Cancer Prev Res 2:450-8).