Isolation of a Novel Latent Transforming Growth Factor- Binding Protein Gene (LTBP-3)

doi:10.1074/jbc.270.17.10147

Isolation of a Novel Latent Transforming Growth Factor- Binding Protein Gene (LTBP-3) (*)

From the (1) Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109-0650, the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, and the
(2) Division of Human Genetics, Department of Pediatrics, Children's Hospital Research Foundation, Cincinnati, Ohio 45229-3039

^§ To whom correspondence should be addressed:
Dept. of Pathology, University of Michigan, MSRB I, Rm. 3520, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0650
. Tel.: 313-747-4774; Fax: 313-936-9353; E-mail: Jeff_Bonadio{at}med.umich.edu.

Abstract

This paper reports the molecular cloning of a novel gene in the mouse that shows structural similarities to the microfibril protein fibrillin and to the latent transforming growth factor-β (TGF-β) binding protein (LTBP), a component of the latent TGF-β complex. The gene was initially isolated during a low stringency polymerase chain reaction screen of a NIH 3T3 cell cDNA library using primers that amplify a human fibrillin-1 epidermal growth factor-like repeat. Three lines of evidence suggest that the mouse gene is a third member of the LTBP gene family, which we designate LTBP-3. First, the deduced polypeptide, which consists of 15 epidermal growth factor-like repeats, 3 TGF binding protein repeats, and 2 proline- and glycine-rich sequences, shows 38.4% identity with LTBP-1 but only 27% identity with fibrillin-1. Second, the gene appears to be co-expressed in developing mouse tissues with TGF-β. Third, immunoprecipitation studies using mouse preosteoblast MC3T3-E1 cells and a specific anti-peptide polyclonal antiserum reveal that the mouse polypeptide forms a complex with the TGF-β1 precursor. Finally, we note that the LTBP-3 gene was recently localized to a distinct genetic locus (Li, X., Yin, W., Perez-Jurado, L., Bonadio, J., and Francke, U. (1995) Mamm. Genome 6, 42-45). Identification of a third binding protein provides further insight into a mechanism by which latent TGF-β complexes can be targeted to connective tissue matrices and cells.

Footnotes

↵* This work was supported in part by the National Institutes of Health (HL-41926 and AR-40586) and by a grant from the Lucille B. Markey Charitable Trust. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank/EMBL Data Bank with accession number(s) L40459.
↵¹ The abbreviations used are:

TGF-β

transforming growth factor-β

LTBP

latent TGF-β binding protein

EGF

epidermal growth factor

EGF-CB

EGF-like repeats with the potential to bind calcium

TGF-bp

a cysteine-rich motif initially identified in the transforming growth factor-β1-binding protein

Fib motif

a cysteine-rich motif initially identified in fibrillin-1

PCR

polymerase chain reaction

nt

nucleotide(s)

PBS

phosphate-buffered saline

p.c

postcoital.
↵²The paper by Li et al. (1995), which refers to the LTBP-2 gene, was in press at the time that the paper describing the human LTBP-2 gene by Moren et al. (1994) was published; these genes are the same.
↵³W. Yin, E. Smiley, and J. Bonadio, unpublished results.