FLRT2 Interacts With Fibronectin in the ATDC5 Chondroprogenitor Cells

Abstract

Expression studies have implicated FLRT2 in cranial neural crest cell migration and prechondrogenic cell condensation during craniofacial skeletogenesis. We aimed to determine whether FLRT2 was involved in mediating cell-matrix interactions in the ATDC5 chondroprogenitor cell line. Immunolocalization experiments of ATDC5 cells revealed that FLRT2 was present on the cell membrane as well as extracellularly, where it colocalized with Fibronectin (Fn). After cell extraction of the matrix, FLRT2 was identified in the ATDC5-derived extracellular matrix (ECM) and was further found to be associated with Fn-coated beads in cell cultures. Blockage of Fn fibril formation via a blocking peptide resulted in a concomitant decrease in extracellular FLRT2 accumulation. Over a 7-day period following the replenishment of the Fn blocking peptide to the cultures, there was a partial rebound in Fn fibril formation that was accompanied by a concomitant reappearance of FLRT2 co-expression. Co-immunoprecipitation confirmed that FLRT2 and Fn interacted, either directly or indirectly. Immunoprecipitation and Western blot analyses with antibodies recognizing epitopes located on the extra- and intracellular domains of FLRT2 further revealed the presence of different sized bands, suggesting that FLRT2 may exist in both membrane-bound and shed forms. Our data therefore provide evidence that FLRT2 and/or its cleavage products may be cooperating with Fn and other ECM proteins to regulate critical cellular events. Further studies will be necessary in delineate more precisely the roles of FLRT2 in mediating cell- and cell-matrix interactions during normal development.

Epigenetically regulated Fibronectin leucine rich transmembrane protein 2 (FLRT2) shows tumor suppressor activity in breast cancer cells

“…FLRT2-fibronection interaction has also been demonstrated in ATDC5 chondroprogenitor cells 24 . Notably, MDA-MB-231 cells did not display strong adhesion to fibronectin-coated beads in cell culture, a protein that shares a high structural similarity with FLRT2.…”

“…During development, all FLRTs are strongly expressed in a subset of sclerotome cells and interact with FGFR1 in the FGF (fibroblast growth factor) signaling pathway 23 . In addition to this function in development, FLRT2 acts as an adhesion molecule by interacting with fibronectin 24 in either a repulsive or adhesive manner. This suggests a possible relationship between FLRT2 and cancer metastasis.…”

Enhanced synaptic plasticity and spatial memory in female but not male FLRT2-haplodeficient mice

“…In addition, the association between LRR-containing proteins and sex hormones activity in the brain 54 , 55 , as well as in other organs 56 – 58 , has been also previously described. Moreover, FLRT2 has been implicated in processes differentially regulated between males and females such as prostate cancer 59 and chondrogenesis 60 – 62 and in several primarily female and hormone-related physiological and pathophysiological processes in humans, including menarche 63 and breast cancer 64 , 65 . In humans, different lines of evidence indicate that some of the differences in the cognitive function -and related pathologies- between males and females can be in part attributed to the differential regulation by sex-hormone signaling 66 – 72 .…”

Rapid Alterations in Perirenal Adipose Tissue Transcriptomic Networks with Cessation of Voluntary Running

“…These changes were associated with an increase in TGFβ mRNA, whose protein has proliferation and differentiation functions [ 17 ]. In addition, transcripts involved in crosslinking such as lysyl oxidase (LOX) [ 19 ], fibronectin leucine rich transmembrane protein 2 (FLRT2) [ 20 ], fibronectin 1 (FN1) [ 21 ], lumican (LUM) [ 17 ], elastin (ELN) [ 17 ], were among the top 15 upregulated with 1 wk of LOCK. This up-regulation in fibrotic transcripts is in agreement with our observed adipocyte hypertrophy, as discussed previously [ 17 ], and is associated with increased local inflammation [ 22 , 23 ].…”