TLN

TLN may refer to:

TLN1

Talin-1 is a protein that in humans is encoded by the TLN1 gene. Talin-1 is ubiquitously expressed, and is localized to costamere structures in cardiac and skeletal muscle cells, and to focal adhesions in smooth muscle and non-muscle cells. Talin-1 functions to mediate cell-cell adhesion via the linkage of integrins to the actin cytoskeleton and in the activation of integrins. Altered expression of talin-1 has been observed in patients with heart failure, however no mutations in TLN1 have been linked with specific diseases.

Structure

Human talin-1 is 270.0 kDa molecular weight and 2541 amino acids. The N-terminal region of talin-1 is ~50 kDa in size and homologous to members of the ERM protein family which have a globular FERM domain (residues 86-400) that links the actin cytoskeleton to adhesion proteins. In addition to F-actin, the N-terminal region of talin-1 binds layilin,β1- and β3-integrin, and focal adhesion kinase. Talin-1 N-terminal region also binds acidic phospholipids for insertion into lipid bilayers. The rod domain (>200 kDa) has considerable flexibility and houses a conserved actin binding site, three vinculin binding sites, and also has an additional integrin binding site, termed IBS2. The head and rod domains are connected by an unstructured linker region (residues 401-481), which houses several sites of phosphorylation, as well as protease cleavage. Talin-1 can homodimerize in an antiparallel fashion, however, talin-1 and its closely related counterpart, talin-2 do not form heterodimers.

TLN2

Talin 2 is a protein in humans that is encoded by the TLN2 gene. It belongs to the talin protein family. This gene encodes a protein related to talin 1, a cytoskeletal protein that plays a significant role in the assembly of actin filaments. Talin-2 is expressed at high levels in cardiac muscle and functions to provide linkages between the extracellular matrix and actin cytoskeleton at costamere structures to transduce force laterally.

Structure

Human talin-2 is 271.4 kDa and 2542 amino acids in length. The size of talin-2 protein is similar to talin-1, and is relatively similar (74% identity, 86% similarity); the size of the talin-2 gene (200 kb) is however much larger than that of talin-1 (30 kb), due to differences in intron sizes. Talin-2 mRNA is expressed in multiple tissues, including cardiac muscle, mouse embryonic stem cells, brain, lung, skeletal muscle, kidney and testis; however expression is highest in cardiac muscle. A detailed analysis of the TLN2 gene revealed that the alternative splicing of TLN2 is complex and encodes multiple mRNA transcripts and protein isoforms. Studies revealed a promoter associated with a CpG island that accounts for most of the TLN2 expression in adult tissues. This promoter is separated from the first coding exon by approximately > 200 kb of alternatively spliced noncoding exons. Interestingly, the testis and kidney talin-2 isoforms lack the N-terminal 50% of the protein, and evidence suggests that this is the isoform expressed in elongating spermatids. Talin is also post-translationally modified via calpain 2-mediated cleavage, which may target it for ubiquitin-proteasome-mediated degradation and turnover of associated cell adhesion structures.