TY - JOUR

T1 - Localization of the transmembrane proteoglycan syndecan-4 and its regulatory kinases in costameres of rat cardiomyocytes: a deconvolution microscopic study.

AU - VanWinkle, W Barry

AU - Snuggs, Mark B

AU - De Hostos, Eugenio L

AU - Buja, L Maximilian

AU - Woods, Anne

AU - Couchman, John R

N1 - Keywords: Animals; Animals, Newborn; Cell Differentiation; Cell Membrane; Cells, Cultured; Cytoskeleton; Extracellular Matrix; Focal Adhesions; Green Fluorescent Proteins; Immunohistochemistry; Isoenzymes; Luminescent Proteins; Male; Membrane Glycoproteins; Microscopy, Confocal; Muscle Contraction; Myocardium; Myocytes, Cardiac; Myofibrils; Protein Kinase C; Protein Kinase C-epsilon; Protein Structure, Tertiary; Proteoglycans; Proto-Oncogene Proteins pp60(c-src); Rats; Rats, Sprague-Dawley; Signal Transduction; Syndecan-4

PY - 2002

Y1 - 2002

N2 - Syndecan-4 (syn-4), a transmembrane heparan sulfate-containing proteoglycan, is unique among the four members of the syndecan family in its specific cellular localization to complex cytoskeletal adhesion sites, i.e., focal adhesions. During early phenotypic redifferentiation of neonatal cardiomyocytes in culture, immunolocalization reveals syn-4 to be heavily concentrated in the perinuclear endoplasmic reticulum-Golgi region, with little found at the peripheral regions. Subsequently, syn-4 becomes localized to a cytoskeletal adhesion complex unique to striated muscle, the costamere. Soon after redifferentiation of myofibrils in cultured neonatal cardiomyocytes, syn-4 is present only in costameres, not in focal adhesions. In cultured adult cardiomyocytes, it is present in both costameres and focal adhesions-the latter in two distinct regions of the spread cardiomyocytes, reflecting localization with two types of actin-containing filaments. The fact that syn-4 is observed early in the costameric regions, as opposed to later in the focal adhesions, suggests that it may play an initial role in early adhesion/signal transduction mechanisms in close proximity to the contractile apparatus, as well as in transmission of contractile force to the collagenous extracellular matrix (ECM) which surrounds the cardiac myofibers in situ. With respect to possible regulatory mechanisms of syn-4, we localized syn-4 with both the epsilon isoform of protein kinase C and the tyrosine kinase pp60(csrc) in costameric regions. These findings suggest that syn-4 may not only play a role in cellular adhesion and contractile force transmission, it may also, through ser, thr, and tyr phosphorylation, be part of an interactive signal transduction mechanism in myocardial functioning via these adhesive cytoskeletal complexes.

AB - Syndecan-4 (syn-4), a transmembrane heparan sulfate-containing proteoglycan, is unique among the four members of the syndecan family in its specific cellular localization to complex cytoskeletal adhesion sites, i.e., focal adhesions. During early phenotypic redifferentiation of neonatal cardiomyocytes in culture, immunolocalization reveals syn-4 to be heavily concentrated in the perinuclear endoplasmic reticulum-Golgi region, with little found at the peripheral regions. Subsequently, syn-4 becomes localized to a cytoskeletal adhesion complex unique to striated muscle, the costamere. Soon after redifferentiation of myofibrils in cultured neonatal cardiomyocytes, syn-4 is present only in costameres, not in focal adhesions. In cultured adult cardiomyocytes, it is present in both costameres and focal adhesions-the latter in two distinct regions of the spread cardiomyocytes, reflecting localization with two types of actin-containing filaments. The fact that syn-4 is observed early in the costameric regions, as opposed to later in the focal adhesions, suggests that it may play an initial role in early adhesion/signal transduction mechanisms in close proximity to the contractile apparatus, as well as in transmission of contractile force to the collagenous extracellular matrix (ECM) which surrounds the cardiac myofibers in situ. With respect to possible regulatory mechanisms of syn-4, we localized syn-4 with both the epsilon isoform of protein kinase C and the tyrosine kinase pp60(csrc) in costameric regions. These findings suggest that syn-4 may not only play a role in cellular adhesion and contractile force transmission, it may also, through ser, thr, and tyr phosphorylation, be part of an interactive signal transduction mechanism in myocardial functioning via these adhesive cytoskeletal complexes.

U2 - 10.1002/ar.10130

DO - 10.1002/ar.10130

M3 - Journal article

C2 - 12209563

VL - 268

SP - 38

EP - 46

JO - Anatomical Record

JF - Anatomical Record

SN - 0003-276X

IS - 1

ER -