Cloning, cellular localization, genomic organization, and tissue-specific expression of the TGFβ1-inducible SMAP-5 gene

SMAP-5 is a member of the five-pass transmembrane protein family localizing in the Golgi apparatus and the endoplasmic reticulum. These proteins have been implicated in intracellular trafficking, in secretion and in vesicular transport. Phylogenetic analyses revealed that SMAP-5 is a member of a small Rab GTPase interacting factor protein family. The human SMAP-5 gene spans about 12.5 kb and comprises 6 exons on chromosomal locus 5q32. The proximal 5′-flanking region of the gene lacks a TATA box and is highly GC rich. Consistent with this, the SMAP-5 gene is expressed in all tissues. The highest level of expression was found in coronary smooth muscle cells, in which expression of the SMAP-5 gene was induced by transforming growth factor β1, thus indicating that this protein may play an important role in inflammation.