Bok is a member of the Bcl-2 protein family that governs the intrinsic apoptosis pathway, although the role that Bok plays in this pathway is unclear. We have shown previously in cultured cell lines that Bok interacts strongly with inositol 1,4,5-trisphosphate receptors (IP 3 Rs), suggesting that it may contribute to the structural integrity or stability of IP 3 R tetramers. Here we report that Bok is similarly IP 3 R-assocated in mouse tissues, that essentially all cellular Bok is IP 3 R bound, that it is the helical nature of the Bok BH4 domain, rather than specific amino acids, that mediates binding to IP 3 Rs, that Bok is dramatically stabilized by binding to IP 3 Rs, that unbound Bok is ubiquitinated and degraded by the proteasome, and that binding to IP 3 Rs limits the pro-apoptotic effect of overexpressed Bok. Agents that stimulate IP 3 R activity, apoptosis, phosphorylation, and endoplasmic reticulum stress did not trigger the dissociation of mature Bok from IP 3 Rs or Bok degradation, indicating that the role of proteasome-mediated Bok degradation is to destroy newly synthesized Bok that is not IP 3 R associated. The existence of this unexpected proteolytic mechanism that is geared toward restricting Bok to that which is bound to IP 3 Rs, implies that unbound Bok is deleterious to cell viability and helps explain the current uncertainty regarding the cellular role of Bok.Bok is a member of the Bcl-2 protein family that controls the intrinsic apoptosis pathway (1-3). Bok contains four Bcl-2 homology domains (BH1-4) 2 and shares greatest sequence homology with the pro-apoptotic proteins Bak and Bax (1-4). However, unlike Bak and Bax, which have clearly defined roles in mediating mitochondrial outer membrane permeabilization (5, 6), the cellular role of Bok is unclear. Key observations that pertain to our current understanding of the function of Bok are (i) that the atypical C-terminal transmembrane (TM) domain of Bok localizes it to membranes of the endoplasmic reticulum (ER) and Golgi (7), (ii) that Bok over-expression leads to apoptosis (7-10) if Bak or Bax are present (7), indicating that Bok lies upstream of Bak and Bax, (iii) that Bok Ϫ/Ϫ mice are phenotypically normal (4, 11, 12), while Bax Ϫ/Ϫ Bak Ϫ/Ϫ mice exhibit multiple severe defects (1), indicating that Bok cannot substitute for Bak and Bax, and (iv) that ER stress-induced apoptosis (13) can be suppressed in Bok Ϫ/Ϫ mouse cells in vitro and in vivo (12), although this result has not been seen by all groups (7). Overall, these data suggest that Bok plays a very different role from Bax and Bak, and that it may participate in the pathway between ER stress and apoptosis.Another intriguing facet of Bok cell biology is that it binds very strongly to inositol 1,4,5-trisphosphate (IP 3 ) receptors (IP 3 Rs) (14), proteins that form tetrameric, IP 3 -, and Ca 2ϩ -gated Ca 2ϩ channels in ER membranes and play a key role in vertebrate cell signaling (15,16). Of the three mammalian IP 3 R types, Bok binding is strongest to IP 3 R1 and IP 3 R2 (14) and the...

Disruptions in neuronal dendrite development alter brain circuitry and are associated with debilitating neurological disorders. Nascent apical dendrites of cortical excitatory neurons project into the marginal zone (MZ), a cell-sparse layer characterized by intense chondroitin sulfate proteoglycan (CSPG) expression. Paradoxically, CSPGs are known to broadly inhibit neurite growth and regeneration. This raises the possibility that the growing apical dendrite is Significance Statement Appropriate dendritic development is essential for normal neuronal function throughout life. The area where most cortical dendrites initially project (the marginal zone) is cell sparse but highly enriched in chondroitin sulfate proteoglycans (CSPGs). While CSPGs are known to inhibit axonal outgrowth, their impact on dendritic growth is unclear. This study demonstrates that the growth of the apical dendrite is also inhibited by CSPGs. However, this inhibitory effect can be reversed by chondroitinase treatment and by activation of the Reelin signaling pathway. Disruptions in Reelin signaling cause intellectual disability and have been linked to autism. Thus, these findings identify a context in which Reelin signaling operates and provide insight into the underlying mechanism of neurodevelopmental disorders.

Graphical abstract

Historically, innovation in the biotechnology sector has relied to a large extent on the expensive infrastructure provided by universities or large pharmaceutical companies. This prohibitive start-up expense is the basis of why garage-style biotechnology entrepreneurs are exceedingly rare as compared to their software and high-tech counterparts. Recent consolidation among pharmaceutical companies and the release of next generation research equipment has produced an affordable surplus in the secondary equipment markets, reducing the barrier to entry posed by equipment expenses. We examine the biotechnology start-up Ichor Therapeutics, Inc., and review strategies that the founding team has successfully employed to establish an affordable laboratory, reduce research expenses, and promote communication among team members.