Proteomic assessment of sympathetic ganglia from adult mice that possess null mutations of ExonIII or ExonIV in the p75 neurotrophin receptor gene.

Neurotrophins, such as nerve growth factor (NGF), are capable of binding to the transmembrane p75 neurotrophin receptor (p75NTR), which regulates a variety of cellular responses including apoptosis and axonal elongation. While the development of mutant mouse strains that lack functional p75NTR expression has provided further insight into the importance of this neurotrophin receptor, there remains a paucity of information concerning how the loss of p75NTR expression may alter neural phenotypes. To address this issue, we assessed the proteome of the cervical sympathetic ganglia from two mutant lines of mice, which were compared to the ganglionic proteome of age-matched wild type mice. The ganglionic proteome of mice possessing two mutant alleles of either exonIII or exonIV for the p75NTR gene displayed detectable alterations in levels of Lamin A, tyrosine hydroxylase, and Annexin V, as compared to ganglionic proteome of wild type mice. Decreased expression of the basic isoform of tyrosine hydroxylase may be linked to perturbed NGF signaling in the absence of p75NTR in mutant mice. Stereological measurement showed significant increases in the number of sympathetic neurons in both lines of p75NTR-deficient mice, relative to wild type mice. This enhanced survival of sympathetic neurons coincides with shifts toward the more basic isoforms of Annexin V in mutant mice. This study, in addition to providing the first comparative proteomic assessment of sympathetic ganglia, sheds new light onto the phenotypic changes that occur as a consequence of a loss of p75NTR expression in adult mice.

Proteomic evaluation reveals that olfactory ensheathing cells but not Schwann cells express calponin.

Human clinical trials have begun worldwide that use olfactory ensheathing cells (OECs) to ameliorate the functional deficits following spinal cord injury. These trials have been initiated largely because numerous studies have reported that OECs transform into Schwann Cell (SC)-like cells that myelinate axons and support new growth in adult rats with spinal injury. This phenomenon is remarkable because OECs do not myelinate olfactory axons in their native environment. Furthermore, these myelinating OECs are morphologically identical to SCs, which can invade the spinal cord after injury. One factor that has contributed to a possible confusion in the identification of these cells is the lack of phenotypic markers to distinguish unequivocally between OECs and SCs. Such markers are required to first assess the degree of SC contamination in OEC cultures before intraspinal implantation, and then to accurately identify grafted OECs and invading SCs in the injured spinal cord. Using two-dimensional gel electrophoresis, we have identified calponin, an actin binding protein, as the first definitive phenotypic marker that distinguishes between OECs and SCs in vitro and in vivo. We have also provided ultrastructural evidence that calponin-immunopositive OECs do not transform into myelinating SC-like cells after intraspinal implantation. Rather, the grafted OECs retain their morphological and neurochemical features. These data yield new insight into the phenotypic characteristics of OECs, which together with invading SCs can enhance regeneration of the injured spinal cord.

Mitochondrial proteomics. Undercover in the lipid bilayer.

Alteration of the mitochondrial proteome and altered mitochondrial function has been implicated in a variety of degenerative diseases, heart disease, aging and cancer. Based upon the human genome there is estimated to be approximately 1000 to 2000 proteins constituting the mitochondrial proteome. Despite the ability of a traditional proteomic approach involving two-dimensional gel electrophoresis (2-DE) to resolve and identify thousands of proteins in a single gel, just over 600 mitochondrial proteins have been identified and characterized at the molecular level. The limitations and recent advances of 2-DE in its ability to study mitochondrial proteins and create a database of the mitochondrial proteome is discussed, as well as the alternative methods that are being employed, including different mass spectrometry based approaches following both one-dimensional SDS-PAGE and gel-free approaches, blue native gel electrophoresis (BN-PAGE), proteome simplification by submitochondrial fractionation, and affinity chromatography. In addition, the successful application of proteomics to the investigation of some specific mitochondrial cardiomyopathies is discussed.