Activity and subcellular compartmentalization of peroxisome proliferator-activated receptor α are altered by the centrosome-associated protein CAP350

Abstract

Peroxisome proliferator-activated nuclear hormone receptors (PPAR) are ligand-activated transcription factors that play pivotal roles in governing metabolic homeostasis and cell growth. PPARs are primarily in the nucleus but, under certain circumstances, can be found in the cytoplasm. We show here that PPARα interacts with the centrosome-associated protein CAP350. CAP350 also interacts with PPARδ, PPARγ and liver-X-receptor α, but not with the 9-cis retinoic acid receptor, RXRα. Immunofluorescence analysis indicated that PPARα is diffusely distributed in the nucleus and excluded from the cytoplasm. However, in the presence of coexpressed CAP350, PPARα colocalizes with CAP350 to discrete nuclear foci and to the centrosome, perinuclear region and intermediate filaments. In contrast, the subcellular distribution of RXRα or of thyroid hormone receptor α was not altered by coexpression of CAP350. An amino-terminal fragment of CAP350 was localized exclusively to nuclear foci and was sufficient to recruit PPARα to these sites. Mutation of the single putative nuclear hormone receptor interacting signature motif LXXLL present in this fragment had no effect on its subnuclear localization but abrogated recruitment of PPARα to nuclear foci. Surprisingly, mutation of the LXXLL motif in this CAP350 subfragment did not prevent its binding to PPARα in vitro, suggesting that this motif serves some function other than PPARα binding in recruiting PPARα to nuclear spots. CAP350 inhibited PPARα-mediated transactivation in an LXXLL-dependent manner, suggesting that CAP350 represses PPARα function. Our findings implicate CAP350 in a dynamic process that recruits PPARα to discrete nuclear and cytoplasmic compartments and suggest that altered intracellular compartmentalization represents a regulatory process that modulates PPAR function.

A Complex of Two Centrosomal Proteins, CAP350 and FOP, Cooperates with EB1 in Microtubule Anchoring

“…Specifically, our data demonstrate that endogenous Cap350 localizes specifically to centrosomes and, to a lesser extent, to spindle MTs ( Figure 1B). In contrast to a recent study detecting CAP350 at centrosomes but emphasizing a role of this protein in the regulation of nuclear hormone receptors (Patel et al, 2005), we could not detect significant amounts of endogenous CAP350 within the nucleus. …”

Recognition of apoptotic cells by macrophages activates the peroxisome proliferator-activated receptor-γ and attenuates the oxidative burst

“…Although mechanistic insights to explain how PPARg might block PKCa activation and subsequent NADPH oxidase assembly await clarification, (in)direct protein-protein interactions of PKCa with PPARg and/or the degree of phosphorylation of PKCa by either attenuating kinases or stimulating phosphatases appear testable approaches. Direct interactions of PPARs with other cytosolic proteins has been shown, 28 which supports the assumption that a similar mechanism may apply to the interaction of PKCa and PPARg. Besides short-term activation as seen in this study, PPARg is also involved in long-term regulation of ROS formation, 29 and thus accounts for an alternative mechanism to regulate ROS production at later time points.…”

Proteome Expression and Carbonylation Changes During Trypanosoma cruzi Infection and Chagas Disease in Rats

“…The observation of increased expression of CEP350 in chagasic rat plasma provides clues to the pathomechanism involved in altered lipid/fatty acid metabolism during Chagas disease. CEP350 is a large centrosome-associated protein with a CAP-Gly domain typically found in cytoskeleton-associated proteins (42,43). CEP350 interacts with other centrosomal proteins (e.g.…”