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TGF-beta 2 （transforming growth factor beta 2） is one of three closely related mammalian members of the large TGF-beta superfamily that share a characteristic cysteine knot structure （1-7）. TGF-beta 1, -2 and -3 are highly pleiotropic cytokines proposed to act as cellular switches that regulate processes such as immune function, proliferation and epithelial- mesenchymal transition （1-4）. Each TGF-beta isoform has some non-redundant functions; for TGF-beta 2, mice with targeted deletion show defects in development of cardiac, lung, craniofacial, limb, eye, ear and urogenital systems （2）.

Human TGF-beta 2 cDNA encodes a 414 amino acid （aa） precursor that contains a 19 aa signal peptide and a 395 aa proprotein （8）. A furin-like convertase processes the proprotein to generate an N-terminal 232 aa latency-associated peptide （LAP） and

a C-terminal 112 aa mature TGF- beta 2 （8, 9）. Disulfide-linked homodimers of LAP and TGF-beta 2 remain non-covalently associated after secretion, forming the small latent TGF-beta 1 complex （8-10）. Covalent linkage of LAP to one of three latent TGF-beta binding proteins （LTBPs） creates a large latent complex that may interact with the extracellular matrix （9, 10）.

TGF-beta is activated from latency by pathways that include actions of the protease plasmin, matrix metalloproteases, thrombospondin 1 and a subset of integrins （10）. Mature human TGF-beta 2 shows 100% aa identity with porcine, canine, equine and bovine TGF-beta 2, and 97% aa identity with mouse and rat TGF-beta 2. It demonstrates cross-species activity （1）. TGF-beta 2 signaling begins with binding to a complex of the accessory receptor betaglycan （also known as TGF-beta RIII） and a?type?II?ser/thr?kinase?receptor?termed?TGF-beta?RII.?This?receptor?then?phosphorylates?and?activates?another?ser/thr?kinase

receptor, TGF-beta RI （also called activin receptor-like kinase （ALK） -5）, or alternatively, ALK-1. The whole complex phosphorylates and activates Smad proteins that regulate transcription （3, 11, 12）. Use of other signalin.