The potential role for Cdc42 protein from rat brain cytosol in phospholipase D activation

Abstract

Phospholipase D (PLD) has been extracted from rat brain membranes and chromatographically enriched 70-fold. From the rat brain cytosol, Cdc42 with a Mr of about 24,000 and ADP-ribosylation Factor (Art) with a Mr of about 18,000 have been purified to near homogeneity. PLD was activated better by purified cytosolic Arf than by the other small G proteins tested. Cdc42 purified from rat brain cytosol showed 70% of PLD activation activity exerted by cytosolic Arf, suggesting that Cdc42 may be one of the major G proteins involved in the activation of membrane-associated PLD. While Cdc42 or RhoA exhibited synergistic activation of PLD when administered in conjunction with Arf, Cdc42 and RhoA showed an additive effect when used together. It is possible that Art" and Rho family proteins may have different interaction sites on PLD. These findings support a role for GTP-binding proteins of the Rho family as well as Arf in the activation of membrane-associated PLD and further suggest that Cdc42 may be a major G protein involved in the PLD activation in rat brain.

cdc42 regulates the exit of apical and basolateral proteins from the trans-Golgi network

“…The association of cdc42 with the Golgi complex is ARF dependent (Erickson et al ., 1996), and ARF has emerged as a key player for recruiting adapter and coat protein complexes to the Golgi apparatus, and for regulating the association of a scaffold of cytoskeletal elements with the Golgi that includes spectrin/ankyrin, myosin and actin (reviewed in Donaldson and Lippincott‐Schwartz, 2000). cdc42 could be participating in the ARF‐dependent coordination of cytoskeletal rearrangements with vesicle formation by activating phospholipid‐modifying enzymes such as PLD and PI(3)K (Zheng et al ., 1994; Han et al ., 1998). As a regulator of COPI activity (W.J.Wu et al ., 2000), cdc42 could indirectly affect the composition of distal compartments of the Golgi complex that receive and recycle vesicles from the more proximal stacks, where COPI is thought to mediate retrograde and anterograde protein traffic.…”

Regulation of Protein Transport from the Golgi Complex to the Endoplasmic Reticulum by CDC42 and N-WASP

“…Endogenous vesicles in extracts occasionally nucleate actin polymerization (Taunton, 2001 for review). Small GTPases of the Rho family regulate actin dynamics through numerous downstream effectors (Hall, 1998) such as members of the Wiskott-Aldrich syndrome protein family (WASP/N-WASP; Aspenstrom et al, 1996;Symons et al, 1996), phospholipase D (PLD; Han et al, 1998), phosphatidylinositide 3-kinase (PI3K; Zheng et al, 1994), and IQGAPs (McCallum et al, 1998) among others. Both PLD and PI3K are involved in the generation of transport carriers and postGolgi trafficking, respectively (Corvera andCzech, 1998, Roth et al, 1999 for reviews).…”

Modulation and Utilization of Host Cell Phosphoinositides by Salmonella spp

“…Although the molecular basis of these events has not been characterized, it has been hypothesized that SopE, which has no inositol phosphatase activity, must activate a cellular phosphatase or phospholipases to increase Ins(1,4,5,6)P 4 levels (59). Indeed, both Cdc42 and Rac, which are activated by SopE, can activate phospholipases (19,22,(55)(56)(57). Altogether, these findings indicate that the actin rearrangements necessary for invasion are the result of a complex series of events involving Rho GTPases and phospholipids or inositol phosphates.…”